Kevin,
Your right it's RIT dye. The way your artical states is pretty close to how to do it. I mix the water and dye very strong and after bringing to a boil I lower it to simmer. You need to get a screen colinder so as to not touch or squeeze the caps. I put them in for about 10 - 15 seconds and out into a pot of cold water next to the hot stuff then back into the hot. This way the plastic dosn't melt on you before in takes on the color. Could take up to four or five times with the red and blue to get them dark enough. Cardinal Red, Royal Blue, Golden Yellow and a double dip into Pink then into Fusha to get the older S-A-F color. It's very messey and you need to have a bottle of clorox spray bleach counter top cleaner handy and LOTS of paper towels. After you do the last dip in cold and have your color right you hit the sink and clean off the surface color. Then dry them off with paper towels. Be sure to cover every area your using and clean spatters right away or you will dye everything you splatter. Multi colored counter tops tend to really p*ss off the wifes. The airtites with the ring seem to hold up the best under the heat. Chuck had some direct fits and they were buggers, melted a lot of them. Jamie Martin tried the new caps with the ridge in them and they all discombubalated in hot water. Seems like the good old airtites are the best for dyeing. Email me direct with any questions and by the way, I save all my dye water in the plastic coffee cans and put seran rap under the lip to seal them. Hope this helps, Jeff