GANTT - Manage or duplicate task colors in the Gantt Chart

Hello,

I would like to make Gantt chart more easy to read.

At the moment, I have introduced some colors with the help of the characteristic "priority" but for me it is not the correct way to deal with.

=> Ideally, I would like to have the possibility to duplicate (or to manage) the color task in the task definition (and to export these colors in the pdf / drawing).

Example : 

In this map, I have defined 2 colors : Green and Yellow.

Current result : 

Expected result :

Have a nice day a thanks for your support,

Yannick LEVENEZ