How to make a proportional color fade / Astera-Tube Color Fade Bug

Hey,

we have the problem that if we let the Astera tubes fade for a long time, 
they feel like they go through all the colors just before they are out.
Someone told me you could set the color fade to "proportional" in the console.
So if, for example, blue is at 100% and green is at 75% and yellow at 10%: the console should first move
blue to 75% and then pull both colors together to 10% and then all 3 Colors together to 0%. (And please without using special times,
this should work quickly even with 6 or more colors)
I think it's an astera bug because it also happens when only one color slowly dims. 
But I don't really remember it. But the function to dim the colors proportionally would still be practical.
 
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