There is somewhere on this forum, a link to a site that has in-game art used in Elite Dangerous, such as the PowerPlay portraits. It also has the rank icons.
If you get a screenshot of someone playing the game, and showing their right-hand panel with the Elite ranks, you can use the pick colour tool (looks like a dropper) in an image editing program, such as Photoshop, to get the colour values and re-colour the blank icons from the site.
I'll look for the site and if I find it, I'll post the link here.
EDIT: I had it bookmarked
http://www.edassets.org/#/