This makes evolution depend on theme-defined named colors, namely:
theme_bg_color
theme_base_color
theme_fg_color
theme_text_color
theme_selected_bg_color
theme_selected_fg_color
theme_unfocused_selected_bg_color
theme_unfocused_selected_fg_color
If it's not defined, then a fallback color is used, in the worse case
one of the fallbacks defined in evolution itself.