One, called cones, addresses color. Distinguishes gross changes in color across entire visible spectrum. More durable, mostly in macula (central vision), and slow to detect change.
The other, called rods, address intensity (brightness). Distinguishes fine changes in light intensity normally presented in gray scale (shades of black and white). More fragile, mostly in prepheral retina, quickly detects change.
RP and Choroideremia tend to kill off the rods in the peripheral retina first eventually moving on to the cones centered in the macula. Fewer rods mean less ability to discerned between changes in shades of color. For example it may be difficult between ruby red and infra red crayons when right next to each other but much easier when separated by florescent yellow.
Or at least that’s the gist of the what I remember from a conversation with a low vision occupational therapist. Can’t really see enough to test it any more.
High contrast is key for anything you need to see right now.
Be careful trusting what you see. Movement, distance, and definition (shape) perception could be off as well