A quick analysis of the various Loctites

[ANOTHERGUN]

Loctite has four (4) RED products, in different strength / formulas. There is the Permanent Strength, High Strength, High Temperature and Large Diameter, (all these are RED)
The lowest torque (to break the bond, and the prevailing torque require to keep the fastener turning) is found on the 'Permanent Strength' formula.
This is designed for fasteners of 3/8" to 1" diameter. The Break Torque is listed as 168 inch lbs. On smaller fasteners, this number decreases rapidly due to the lack of surface area. Stainless steel typically does not reach these values unless you use their 'Primer/Cleaner'.
This product, when found in a liquid (squirt bottle), works in the absence of air. The act of assembly pushes out the air, then it will setup, about 20 minutes, and fully cures in ~ 24 hrs. Basically forms a hard a kind of plastic. Any loctite that happens to smear atop the steel can simply be wiped up. The fasteners need to be free of oil / grease. Not for use on plastics, and I would not want to try it on polymers either.
True, heat will help making removal easier. But you do not need a torch. If necessary, a soldering tip or a wood burning handtool will work.
The idea is to cover the first 3-4 threads (it comes out relatively thin). Assemble the parts and allow it to cure. There is an added benefit to Loctite, since it seals the assembly with this plastic type of material, it helps to keep water /moisture out, thereby helping prevent rusting, which would be a bear to get apart.
I would try the blue for simple keep in place fasteners, and go to the red for rough service, heavy recoil or problems loosening.
If you disassemble the parts, it is not necessary to clean out the 'old' loctite. Another drop or 2 is all that you need.
If you can find it,...there is A Purple Loctite that is probably the best answer. It is for #2 to 1/4" screws and list the break torque @ 62 inch lbs.
I would recommend against the Green Loctite in this type of application.
T.M.I. ??? Sorry !
Good luck!

[Hawkmoon]

Several posts have referred to using Loctite® for various purposes, and in some of the posts the grade of Loctite® has been referred to by color. But this is imprecise, at best. As was pointed out in one of the discussions, the Loctite® web site is virtually useless as far as end users such as us finding any guidance as to which product we might want to use for a particular application.

The information contained in the post above didn't make sense to me (first time I ever heard that they have four Red products, with differing strengths, for example). And I've been using Loctite products for more years than many of you have been alive.

So—being the ancient curmudgeon that I am—I reverted to obsolete technology. I picked up the telephone (desktop, wire connection to a land line) and called Loctite® to request a real, honest-to-goodness catalog. Some of you may remember such artifacts. They are printed on paper, with ink, and provide all sorts of often-useful information without having to scroll and click and surf and “drill down” through ten thousand layers of counter-intuitive menus only to find that you can’t get the information you need from the web site.

The information we need is right there in the catalog, neatly summarized on page 96. In the interest of posterity, here’s the summary version:

Loctite® 220™ Threadlocker
Low Strength / Wicking / Blue
A low viscosity threadlocking adhesive that allows the product to wick along the threads of preassembled fasteners. Perfect for fasteners up to ¼” diameter (6mm).

Loctite® 222MS™ Threadlocker
Low Strength / Purple
Perfect for small fasteners up to ¼” diameter (6mm), long engagement length fasteners, and components requiring occasional adjustment. Apply to threaded parts before assembly. Parts can be disassembled with hand tools.

Loctite® 242® Threadlocker
Medium Strength / Removable / Blue
Removable strength, general purpose threadlocking adhesive especially well suited for fasteners between ¼” to ¾” diameter (6mm to 20mm). Applied to threaded components before assembly. Loctite® 242® Threadlocker has controlled lubricity for accurate clamp loads. Parts can be separated using hand tools.

Loctite® 262™ Threadlocker
High Strength / Red
A high strength product that is applied to fasteners up to ¾” (20mm) in size before assembly. Localized heat and hand tools are required to separate parts. Solvents will not weaken the adhesive bond.

Loctite® 290™ Threadlocker
Wicking / Green
A low viscosity, threadlocking liquid that wicks along the threads of preassembled fasteners to secure them in place. Seals porosities in welds and metal parts. Ideal for fasteners ranging from #2 to ½” (2.2mm to 12mm) in size. Localized heat and hand tools are needed for disassembly.

In addition to the above, which are their traditional products, they also have two new versions that come in “glue stick” form:

Loctite® QuickStix™ 248™ Threadlocker
Medium Strength / Removable / Blue
New, patented semi-solid stick formula offers added convenience and portability. Like Loctite® 242®, this threadlocker stick is well suited for ¼” to ¾” (6mm to 20mm) fasteners and is removable with hand tools. The semi-solid formula also means it won’t spill or leak.

Loctite® QuickStix™ 268™ Threadlocker
High Strength / Red
Revolutionary semi-solid stick formula is high strength and best suited for fasteners up to ¾” (20mm). Semi-solid formula offers added convenience and portability. Localized heat and hand tools are required to separate parts.

[1911Tuner]

The Hawkman's nailed this'un. Ain't but one red LocTite...It ain't the color of the tube...It's the color of the stuff IN the tube. Numerical ID is the guide to use. Avoid the green stuff unless ya want it there dang near forever!
(Axe me how I knows dat.)

[Gammon]

The above list is incomplete and possibly misleading. The green "wicking" sealant referred to is not all that hard to remove, and is great for setting a rear sight in place after it has been adjusted. Much easier than applying the sealant in advance of the sighting in and hoping that it won't set up before you're done. There is another green Loctite (stud and bearing mount, I believe) that is used for permanent installations and is a bear to remove. The grades of LocTite are accurately listed above, but they are only a sampling of what is available. Also all of these sealants become much more effective when used with the primer.
PS There are several red loctites, and I'm not talking about the tube.

[Konza]

Threadlocker Liquid Adhesives

Prevent threaded metal fasteners from loosening due to shock and vibration. These anaerobic adhesives also seal against fluid leakage, prevent corrosion between threads, and withstand most solvents, chemicals, and harsh environments. Come in bottles. Low and medium strength can be removed with a hand tool. High strength require heat and a hand tool.
222MS™— Low strength for 1/4" dia. and smaller fasteners. NSF-P1 certified for food processing areas.
242®— Medium strength for 1/4" to 3/4" dia. fasteners. NSF/ANSI-61 certified for use with drinking water systems.
243™— Medium strength and oil resistant for fasteners 1/4" to 3/4" dia. NSF/ANSI-61 certified for use with drinking water systems.
246™— Medium strength for fasteners 1/4" to 3/4" dia.
262™— High strength for fasteners up to 3/4" dia. subject to high vibration and shock. Resistant to oils. Great for Grade 5 and 8 fasteners.
266™— High strength, withstands temperatures up to 450° F, and resists surface contamination for fasteners up to 3/4" dia.
271™— Very high strength for up to 1" dia. fasteners. Ideal for harsh applications and tamperproofing. UL listed.
272™— High strength for bolts up to 1 1/2" dia. in temperatures up to 450° F.
277™— High strength for use with fasteners up to 1 1/2" dia.
290™— Medium strength for locking already-assembled fasteners up to 1/2" dia. NSF/ANSI-61 certified for use with drinking water systems.
425™— Low strength super glue (cyanoacrylate) for locking metal and plastic fasteners. Use before or after assembly.
2432™— Medium strength and low sulfur for sensitive metals such as titanium.
2440™— Medium strength and does not require primer.
2760™— Exceptionally high strength, even on oily unprimed fasteners. Use for heavy duty applications, such as construction and railroad equipment, where shock and vibration are prevalent.

Retaining Compounds

For nonthreaded metal cylindrical parts such as shafts, hubs, bearings, bushings, splines, and pulleys. They prevent corrosion and fluid leakage between surfaces, resist most chemicals, allow reuse of slightly worn parts, and provide better strength than shrink-fit and press-fit assemblies. Come in bottles.
603™— High strength and contaminant resistant. Fills spaces up to 0.005" dia.
609™— High strength and low viscosity (125 cp). Fills spaces up to 0.005" dia.
620™— High strength, high viscosity (8500 cp), and high temperature. Fills spaces up to 0.015" dia.
638™— Maximum strength. Fills spaces up to 0.015" dia.
648™— High strength. Fills spaces up to 0.006" dia.
680™— High strength and medium viscosity (1250 cp). Fills spaces up to 0.015" dia. NSF/ANSI-61 certified for use with drinking water systems.

Threadlocker Stick Adhesives

Same performance as our other threadlockers, but in a convenient stick form. Begin to harden in 10 min. Max. temperature is 300° F.
248™— Medium strength for 1/4" to 3/4" dia. fasteners. Color is blue.
268™— High strength for heavy duty applications on fasteners up to 3/4" dia. Color is red.