Rated 4 out of 5 stars

A star off because I HAD to do it myself...
In config editor find the line: extensions.minCompatibleAppVersion, and change the value to 0.3.

Worked for me immediately! Be nice if the author would update this really cool add-on.

Rated 5 out of 5 stars

Works on Thunderbird 10.0, after modifying the max version # in the install.rdf file. The how-to looks complicated, but it's straightforward.

I would like that Mozilla changes its stupid major release frenzy.

Rated 5 out of 5 stars

Install Quote-Colors to current the versions of Thunderbird and SeaMonkey
01. Create a new folder named Work
02. Copy quote_colors-0.3-tb+sm.xpi to the Work Folder
03. In the Work folder rename quote_colors-0.3-tb+sm.xpi to quote_colors-0.3-tb+sm.Mod.xpi.zip
04. Extract the following folder from the quote_colors-0.3-tb+sm.Mod.xpi.zip file: install.rdf to the Work Folder
05. In the Work folder open the install.rdf file in your text editor.
06. Go to Line 11 in the file or search for <em:targetApplication>
07. For Thunderbird, Go to Line 16 <em:maxVersion>#.*</em:maxVersion>
08. Change the # for the line to the current version, leaving the .* (e.g. for Version 10.2 it should read <em:maxVersion>10.*</em:maxVersion>
09. For SeaMonkey, Go to Line 24 <em:maxVersion>#.*</em:maxVersion>
10. Change the # for the line to the current version, leaving the .* (e.g. for Version 10.2.5 it should read <em:maxVersion>10.*</em:maxVersion>
11. Save the file in the Work Folder, ensuring it maintains the name of install.rdf
12. Copy install.rdf into the compressed file created in Step 03 above.
13. Verify to overwrite the existing file in the compressed file created in Step 03 above.
14. Rename quote_colors-0.3-tb+sm.Mod.xpi.zip to quote_colors-0.3-tb+sm.Mod.xpi
15. Open the desired application (Thunderbird/SeaMonkey)
16. Select Tools->Add-ons Manager
17. Select the option Install Add-on from File
18. Browse to the Work folder
19. Select the modified add-on installation file: quote_colors-0.3-tb+sm.Mod.xpi
20. Click okay and follow the prompts to install.

Thanks to @Robert Kofler https://addons.mozilla.org/en-US/thunderbird/user/5914218/ and @Mozzied https://addons.mozilla.org/en-US/thunderbird/user/4710265/ for giving me the pieces to get this great add-on to work with SeaMonkey 2.6.1

Rated 5 out of 5 stars

Hi, all. You can use it after ThunderBird 8.*.
set extensions.checkCompatibility.8.0 as false,
for other versions of ThunderBird, set these keys as false.

extensions.checkCompatibility.5.0
extensions.checkCompatibility.6.0
extensions.checkCompatibility.7.0
extensions.checkCompatibility.8.0
extensions.checkCompatibility.9.0

But I hope to see a Real Update...

Rated 4 out of 5 stars

After I went to 2.5 and beyond I too can not use QuoteColors. at the rate the SeaMonkey Group is going we will be up to 3.0 by June. You need to get this fixed ASAP. People with Eyesight problems (like me) depend on this extension.

Rated 5 out of 5 stars

I used this extension for long time on my Seamonkey but after updated to 2.5 today, I can't made it work :( is a nice one, like to use it again

Rinne an t-úsáideoir seo léirmheas ar an mbreiseán seo cheana.

Rated 5 out of 5 stars

Just upgraded to Thunderbird 8.0b2 and it no longer works, even with compatibility reporter. Hopefully we'll see an update soon.

Rated 5 out of 5 stars

Nice Add-on! I just found out that you can combine Quote Colors with QuoteCollapse so that you can have both features at the same time!

Rated 5 out of 5 stars

I got Vim from here: http://www.vim.org/download.php#pc
I got the unzip and zip from here: ftp://ftp.info-zip.org/pub/infozip/win32/
Check the readme to see which files you need.
I saved them to the Tbird extensions folder.

Vim wouldn't save the modified install.rdf into the .xpi past 87% (it isn't read-only or blocked and I have admin rights), so I had to jump through hoops:

1. rename quote_colors-0.3-tb+sm.xpi with .zip extension
2. unzip to dedicated folder (to avoid confusion)
3. right click install.rdf, Edit with Vim
4. save file
5. zip the quote_colors folder contents with 7-zip
6. rename the new .zip with .xpi extension
7. open Tbird and install .xpi

Rated 1 out of 5 stars

I'ts not working in 10.0a1 ^(

Rated 5 out of 5 stars

To: Robert Kofler

Thanks for sharing the great way!

Rated 5 out of 5 stars

great tool - gives structure to endless replied & replied emails ;-)

but how to install on thunderbird 6/7/8/.. and higher?
well, use vim, which is able to edit ziped xpi files.
vim quote_colors-0.3-tb+sm.xp
inavigate to: install.rdf
and change <em:maxVersion>7.*</em:maxVersion>
save & install it!

Rated 5 out of 5 stars

I do confirm. I works with TB 6 without a single problem. Just modify the max version to 6.0 instead of 3.0 of the rdf file after unzipping the XPI.
http://forums.mozillazine.org/viewtopic.php?f=18&t=1367355

Rated 3 out of 5 stars

Open the xpi-file. You have to edit the install.rdf file. Change the line <em:maxVersion>3.0.*</em:maxVersion> into <em:maxVersion>6.0.*</em:maxVersion>

Rated 5 out of 5 stars

Very useful extension, though I wish it supported more than five levels (I get some very nested conversations at times). Like jk2jxl, I was able to change the maxVersion value in the install.rdf file and install it in Thunderbird 5. See http://kb.mozillazine.org/Editing_an_add-on_to_change_its_compatibility if you want to do this.

Rated 5 out of 5 stars

It moved with Thunderbird5 without trouble.

Rated 5 out of 5 stars

Seems to work fine with Thunderbird 5 (just need to set compatibility). Hopefully we'll see an official update for this soon.

Rated 4 out of 5 stars

Quote Colors is a very useful add on.

Does work with any Tbird version over 3.1.+. Using 3.1.10 here.

Rated 5 out of 5 stars

Should be a build in feature for the next Thunderbird!

Rated 5 out of 5 stars

Makes it so much easier to visually differentiate who wrote what. Especially in e-mails that were sent forth and back a lot of times. Something that I missed a lot in Thunderbird before I installed this add-on