[ADDED] Colour tool in preview to show which extruder in use

[RodLaird]

There is no way to tell whether you have correctly allocated extruders in the preview - that I can see. (Advice if I have this wrong)

Setting a different colour to the tool preview (which is in any case selectably viewable) would be an immense help...

[TenKOhms]

you're correct, the colors in the G-Code Previewer are solely based off of print speeds

[ole_blue_moon]

I second your recommendation. Print preview should include colors for both the object and support when using 2 extruders. Would help when trying to verify extruders/color switches at the proper point in the print. I find the colors shown for speed to be of minimal value at least so far, maybe later when speed of print becomes more important to me.

[RodLaird]

To clarify, my suggestion is to just change the colour of the "tool" when it is visible... Not necessarily the extruded material...

[S3D-Jason]

This feature was addd in version 3.0. Just select "active toolhead" coloring in the preview mode.