The main challenge would be to make everything small and flexible enough so that it can be attached to the (exterior of the) helmet.
As for the schematics, you can go with the 595-based solution or adapt the one used in MeggyJr RGB (one 8x8 RGB == 3 x 8x8 single colour).
The power could come from a LiPo rather than 6 AA eneloops (why not 4?), since it packs a similar capacity in a smaller package.
Please keep us posted with your progress.