I spraypainted bobbins once, dead easy but if you want it to hold up to use it will need to be finished with a hard clear coat. I didn't, and it looked good for about a week or less.
Of course, bobbins in multiple colors abound on eBay/Amazon but you have to wind them yourself! I'm attempting to build a DIY sustainer driver for an upcoming Warmoth build and want a non-standard color to set it apart from the actual pickups.
Other thoughts... stickers, contact paper, extremely thin veneers, mylar, lots of options! Peruse art/craft books at your local library.
For the rings... acrylic paints (hand painted), dip/swirl, distressed metal, wood (DIY or eBay for existing products). I'm awaiting an order of herringbone purfling to wrap around the rings of a set of humbuckers.