It would be cool if the labcolor()-option from the sunburst-package can be ported to treemap (asjadnaqvi/stata-sunburst#3 (comment)).

Dear @asjadnaqvi, I propose the following changes to the code:
Insert after line 673

            mata: S = ColrSpace()
            mata: S.colors("black `r(p`clr0'name)'")
            mata: st_local("contrast_black",strofreal(S.contrast((1,2))))
            
            if `contrast_black' > 4.5 {
	            local mlabcolor "black"
            }
            if `contrast_black' <= 4.5 {
	            local mlabcolor "white"
            }

Then change all mlabc(black) into mlabc(mlabcolor')`

I tested it with my use case and it works.

My code above only works with named colors. I try to find a way to get the RGB values working...

Marc, can you give an example figure to show what you are trying to do?

Of course:
My own program is called treemap2:

cwf default
cap frame drop auto
frame create auto
cwf auto
sysuse auto

split make, parse(" ") gen(brand)
ren brand1 brand
egen model = concat(brand2 brand3)

treemap2 weight, by(brand model) ///
		addtitles palette(hhu_color_fak) ///
		name(brand_model, replace)

With the palettes that do not use named colors - it does not work. But I am a Mata Newbie - so no clue how to do it the best way. It should be possible to add the RGB into the color list and then to contrast them...

Ok so for darker background colors, the label color should be lighter in order to increase the contrast for readability.

I prefer having a generic solution that can be added to all packages. For sure it will be very useful. For example bimap, labels are not visible with darker colors. I will have a look!

This code-addition also works with the tableau-palette without named colors:

            mata: S = ColrSpace()
            mata: S.colors("black")
            mata: S.add_Colors("rgb `r(p`clr0')'")
            mata: st_local("contrast_black",strofreal(S.contrast((1,2))))
            
            if `contrast_black' > 4.5 {
	            local mlabcolor "black"
            }
            if `contrast_black' <= 4.5 {
	            local mlabcolor "white"
            }