I've experienced the same. I don't have impaired eyesight or color blindness, but the markers are difficult to see.

One of the major problems I found is that they all have that outer glow effect, which makes them blurry and difficult to visually parse. One quick, simply improvement that could be done is just make them a solid color, sharp edges, no blurry effects. You can keep the blue hue for odds and magenta for evens.

Another quick fix would simply be making the arena floor stone grey instead of orange.