Multicolor question
I have one question for prusaslicer. is it possible to print in 2 color in the same layer with manuel color change ? exemple in white print text and after make color change and switch to black for rest of layer ?
RE: Multicolor question
Simple Answer, Yes
However,
White printed in front of black, tends to look grey in many instances.
White comes in MANY Opacities... for lithophanes low opacity is good, in this use case, you want a really opaque white.
I don't remember the manufacturer, I got a roll of 'Signal White' filament, it is really opaque.
this is an old post but it covers some of the steps.
https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/acting-as-my-own-mmu/ 
Rainer also has a post on the subject
Regards Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE:
Follow Joan's advice. It takes a bit to set up but it works well. You want to make sure that your printer is well calibrated and I usually turn elephant foot compensation off to avoid artifacts in the first layer.
As Joan hinted at, this technique works better for some colors then others. Light colors such as yellow or white against dark background can be a bit of a challenge and you may need 3 or more layers of those colors. And of course the more layers, the more color swaps....
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...