Let me echo @slimsag and say try not to rely on people differentiating things by color. Labels, titles, alt text, etc is probably useless because a lot of times

Let me echo @slimsag and say try not to rely on people differentiating things by color. Labels, titles, alt text, etc is probably useless because a lot of times the problem is I don't see that there's a control to investigate at all. Add a different shape, size, outline, or if it really has to be color only make the difference be not just hue but saturation and luminance as well.