To reproduce:

• Choose a Workboard, select Change Background, pick a color (like "Blue") not a gradient.
• View workboard.

Expected behavior:

• Background is blue.

Actual behavior:

• Background is still grey, although frame has adjusted to white text, as though color was present.

I think this is because phui-theme-dark and phui-workboard-($color) have the same strength and fight:

If this is a pain to fix, one junk workaround I could imagine is to use linear-gradient to give the flat colors a "gradient" background image from, say, blue to the exact same blue.