How to find four equally contrasting colours that are appealing to the eye?
I have a plot for a scientific argument I'm trying to make. There are four colours that should be (roughly) equally contrasting with two others. ie, if the colours are A-D, then A and B should be roughly as contrasting as B and C, and C-D, and D-A. A-C should be about the same as B-D...
Basically for starters I chose a bright red, green, yellow, and blue. This makes my point well, but looks pretty bad. I find it quite harsh. Do you have any ideas for how to improve this? My thought, not yet implemented, is to do black, gold, white, and purple.
The problem with your red, green, blue, yellow set is that is all the colors. You can make every color by mixing those. A more limited color set will likely look better.
Red and green are not directly contrasting colors. You would want red and cyan. Other contrasts are blue and yellow, or green and magenta.
But you are talking about pleasing the eye. That is art, not science. So you should consider just trying a few color combinations until your eye is pleased and your scientific point is still expressed. If you create 4 squares in a grid in a graphics tool (on the background color you will be using) and work with various colors and tones until you have a set that is both distinctive from each other yet pleasing to look at together that will likely get you the best result.
There are online tools specifically for designing color sets.