I have a couple different kits from pearlx that Nick mentions. These are super strong colors and easy to get some wild pearl colors using a relatively small amount of the powders.
I also have a bunch of pearls from this site:
http://www.paintwithpearl.com/. Using about 1/2 of what one would normally use to get the sheen of a regular hi lite, these colors are super potent. One of the colors, pink tangerine, works super well in fluorescent orange...very minute amount.
For the best general plastic use, I suggest using the hi lites that are available at Do-It or other sites where plastic additives are sold. These are formulated and marketed for this specific use. The peripheral products like what Monte, Nick and I have brought to light tend to be very, very strong and change things in a hurry and should be used sparingly. My first attempt at pearlx was using a brownish bronze in brown watermelon. It was a 4 ounce batch and a matchhead size dollop of the bronze turned the whole batch opaque pearl green-brown. Had I wanted a pearl color, it would have been great, but I wanted a transparent color. On a subsequent try I used about 1/4 of what I used the first time and it was close but still stronger than I wanted.
There are times when separating pearl from hi lite is tough but using the right amount of hi lite will result in plastics with the sheen like what some of Monte's and efish show.
