they are... any white nylon wheel can be dyed.. i use RIT dye that can be found and any walmart in the laundry section... its cheap.. like a buck or something and wall mark has a huge selection of colors

i usualy boin in a big pot and tie some wheels to a string and then to a coat hanger... after the water is at a fast boil, pour in the power dye mix and turn the heat down so that it just barly keeps the water moving dip the wheels in and make sure you get the water completely over them.. check in about 5 min.. and pull out in about 10 min
http://www.youtube.com/watch?v=AKy-OGGtU1o
http://www.youtube.com/watch?v=vPfidyeeS1M