What do the different colors signify in the diep.io class chart?

If you look at the class chart shown on the diep.io wiki, you'll see there seems to be a color coding scheme using yellow, blue, red, and green, but there's no key. Can anyone explain what the different colors indicate?

Solution 1:

Not definitive, but as mentioned on the wiki

Interestingly, there is a recurring pattern of colors in the upgrade selection menu and the Class Tree. The first tank will always have a light blue background. The second will be green. The third will be red. The fourth will be yellow. The fifth will be dark blue, and the sixth will be purple (This order can be found in tank's add stats buttons which are color-reversed). Regardless of speculation, colors do not seem to represent anything other than a simple order pattern to more easily discern tanks apart when quickly selecting an upgrade

Note that Tank->Twin is light blue, and adds an forward extra barrel, while Machine Gun->Gunner has a similar effect, but in a different color.

It is interesting that tanks which appear in multiple paths (Twin Flank and Quad Tank) have the same color both times, but they have been placed in the same order to keep the pattern.

Image below for observing the tank pattern.