There are lots of options, like making gradients of different colors.
Playing with the color choices, I came with this one:

What I did was setting the first color to 150 hue, 150 sat, 0 lum. Then I added a color with 150 hue, 150 sat, but increasing the lum 10 by 10 (step 10), until I got to lum=210. That way the colors were really vivid in a shade of blue.
It would be great to see other combinations of colors, there's a lot of creativity in the color scheme of this element.







