I have switched to "Unbranded Builds" Rated 5 out of 5 stars

Firefox Unbranded Builds
Link: https://wiki.mozilla.org/Add-ons/Extension_Signing#Unbranded_Builds

I am using Anycolor modified v0.3.9 with "Unbranded" 48.02...works fine with Q Mark's instructions below (August 19, 2016).
Also Waterfox 48.01 and Dev 50.0, it has now completely stopped working with Firefox Release 48 and above and Betas.

Modified v0.3.9 still working for me with Firefox 49.0a2 Developer Edition 64 bit, Firefox 47 64Bit, Firefox 47 and Waterfox 64 bit 46.0.1....... Rated 5 out of 5 stars

See my other posts for more info....
But to make it work your will have to go to about:config & look for "xpinstall.signatures.required" (no quotes) & Double-click on the preference name so that its value is set to false. Now you can install unsigned extensions in Firefox. A browser restart is not needed.
"Classic Theme Restorer" AddOn helps it work best.
Direct link to manbat's modified V0.3.9: https://groups.google.com/group/firefox-add-on-anycolor/attach/d87daf654b4c0849/anycolor-0.3.9-fx-win.xpi?part=0.1&view=1

Modified v0.3.9 still working with Firefox 40.0.2, Developer Edition 64 bit and Waterfox 64 bit....... Rated 5 out of 5 stars

I have been maintaining this for my personal use. I have been able to make it function on all versions up to Firefox 42 Developer Edition 64 Bit. I guess that soon I will not be able to use it on the release version because "unsigned Addons" will soon not be able to be installed on "Release Versions and Betas". I hope over-ride ability is still left on the Developer Edition 64 Bit.

Modified v0.3.9 still working with Firefox 39, Developer Edition 64 bit and Waterfox 64 bit.....If anyone is still interested......Anycolor v 0.3.9 is still working on Firefox 39. I have modded my Install RTF to 90.
Google Groups link on how to modify: https://groups.google.com/forum/?fromgroups=#!topic/firefox-add-on-anycolor/ShwiBcmOIdA
"Classic Theme Restorer" AddOn helps it work best.

Still working with Firefox 29.... Rated 5 out of 5 stars

Still working With Firefox 29.........Had to add the "Classic Add On" to get the old menus and button styles. Then had to redo a few preferences, but now it is back the way I like it. I had previously modded my version of AnyColor to install to all the way up to "Firefox 40"......lol. So we see how much longer I can keep it working...lol

How to modify Anycolor v0.3.9 tp work with Firefox 29 Rated 5 out of 5 stars

1. Download Anycolor v0.3.9 from mediafire link below in Que mark's post. 2. Open the anycolor-0.3.9-fx-win.xpi with 7zip 3. Click on the install.rdf 4. Look for maxVersion> 5. Change it to 29.0.* ( I went ahead and changed to to 40.0.* ...lol) 6. Install the modified xpi in Firefox 29.....Should work now.********************************************************************** Works great for me !!!

There really is an AnyColor 0.3.9 !!! Rated 5 out of 5 stars

There really is an AnyColor 0.3.9 !! Thanks for the link!! Works fine on Nightly 20 also!!(After a quick edit) Only issue I have found is that if you have too many Tabs open the Pinned App Tabs "stack up"(Edit:Figured out the stacking,Just drag the top one to the left and they rotate.).... GREAT...I Have Missed it!!

v 0.3.8c Available!! Rated 5 out of 5 stars

AnyColor does indeed live again!! I am using it on 6,7 and 8 (no longer works on Firefox 9 and above. Hoping for another update!!!) . Works great and has a few new mods also. Available as mentioned below!! Version 0.3.8c now available (Unofficially)...but still GREAT!!!