first steps towards brand-specific color schemes

CONFIG.md

@@ -161,6 +161,10 @@ Needs about 65 bytes of ROM space to handle both joysticks.
 
 ## Eye candy
 
+### `CONFIG_COLORS_BRAND`
+
+Tries to adjust the color scheme to the selected brand. Some brands might not support this.
+
 ### `CONFIG_BANNER_SIMPLE`, `CONFIG_BANNER_FANCY`, `CONFIG_BANNER_BRAND`
 
 Select startup banner - either a simple one, or with some colorful elements. `CONFIG_BANNER_BRAND` heavily depends on the selected brand, not all the brands support it.