There are essentially three parts there:
1) the plugin to convert an "audio" tag or RSS enclosure to the code to load a Flash player.
2) the very nice Flash player.
3) some backend stuff for picking and storing colour settings.
Parts 1 and 3 are doable, but require a fair amount of work - and if you just want to use the Flash player, unnecessary.
It would be fairly straightforward to cobble together a snippet that would output the code for the Flash player, called like so:
[[FlashAudioPlayer? &audio=`name_of_mp3_file1.mp3`]]
with colours either passed through in the call or in the snippet code itself.
If you can obtain permission from 1 Pixel Out to use the flash file and distribute it in a MODx add-in, then I’ll happily sort out the basic MODx snippet and package.