On making dark mode consequent i found that if you use set/putbitmap and give it a black color, it won't be seen on a black background.
Now you can use
setbitmap(bitmap, -1); it will automatically use the foreground color
Another wayt is using command(FUNCTION, 43, x, 0) where
x = 0, returns current background color
x = 1, returns current foreground color
x = 2, returns current font color
So if you use
int mycolor = command(FUNCTION, 43, 1, 0);
setbitmap(bitmap, mycolor);
it will also always be visible.