See my post in the following thread link where you can currently set Gmail “Outline Folder colors” via eM Client Tags.
There is also an option to “color the folder name” via “Menu / Settings (Preferences) / General / Folders / Color” Use folder color for icon and text. That way the color will stand out more.
Lastly if you prefer “Solid folder colors” like Gmail online, there is a Sleekplan suggestion for that which you can vote for via the following page.