potentially color-blind person: how to choose colors for a graph

I have a chart with 5 curves (curves 1-5). A person told me that colors 1 vs. 2 as well as colors 3 vs. 5 are difficult to distinguish. While I can understand that 3 and 5 are somewhat similar, the 1 and 2 are completely different in my view. I do not know, maybe this person color-blind. But I need to make the graph so that he will be able to distinguish the colors. My problem is that I have only 7 colors in total (additional two colors are 6 and 7). I did not use the yellow (6) originally because it is too faint in my view. The cyan (7) also is similar to blue.

How you would suggest me to choose the colors? The proximate curves should clearly have the most distinguishable colors.

Thanks!