Gcolor3 is a color selection dialog written in GTK3. It is much alike Gcolor2, but uses the newer GTK version to integrate better in your modern desktop. It has the same feature set as Gcolor2 and even uses the same file to save colors for compatibility reasons.
Sorry for the spelling and phonetic errors in the text.
Owner and main writer of MintGuide.org is not a native English speaker.
Gcolor3 is a simple color selector that was originally based on gcolor2, ported to use GTK3.
Installation Gcolor3 into Linux Mint:
cd /tmp; wget https://www.dropbox.com/s/3zyy25freu8ovz9/gcolor3_1.2.1ubuntu1_i386.deb; sudo dpkg -i gcolor3_1.2.1ubuntu1_i386.deb
cd /tmp; wget https://www.dropbox.com/s/ojc1uttm9rgfk76/gcolor3_1.2.1ubuntu1_amd64.deb; sudo dpkg -i gcolor3_1.2.1ubuntu1_amd64.deb
On my Linux Mint Mate it worked perfectly. On a virtual machine in Linux Mint Cinnamon color was not going. Can't say why.
Gcolor2 also worked without problems on mate, but the cinnamon color is not collected.
If you want you can install Gcolor2:
sudo apt-get install gcolor2