I'm colorblind and I usually don't have an issue with flat design. I rather like it. I do tend to rely more on light/dark than hue, and if a hue is too similar

I'm colorblind and I usually don't have an issue with flat design. I rather like it. I do tend to rely more on light/dark than hue, and if a hue is too similar, light/dark is my only visual cue. For example, in similar shades of red and green, red usually "looks darker."