This is probably "more than you ever wanted to know" about dyeing canopies, but it was an easy cut'n'paste from an RC club newsletter, so what the heck, here it is in its entirety. Apologies for the length to those who aren't interested, but I'm too lazy to edit it down :-)
Ever wonder how those great looking tinted canopies got that way? In many cases, the builder dyed the canopy using dyes intended for tinting clothing! The process is actually quite easy, and the dye itself is easily obtained and quite cheap. I've found that Ritt powdered dyes are quite effective in tinting the plastic canopies found in most model kits, and are available in most drugstores, priced around $2 per package. When using powdered dye to tint plastic canopies, here are some tips to consider:
Make sure that the canopy is squeaky clean before dyeing. Washing in mild dishwashing detergent is effective here, and will avoid unsightly fingerprints in the final work. Dry using a soft cloth (not paper tooling, which is almost always abrasive to some degree).
The container used for dyeing must be clean as well. Stainless steel or glass containers are the best for this process. Use a container that is just large enough to allow the canopy to be fully immersed in the dye bath.
Wear something appropriate for working with dye. It is also a good idea to place the dyeing container within a stainless sink and to clear any items from the working area. If you do splash some dye on a hard surface in your work area, some diluted bleach will take the stain out (rinse the area thouroughly with water after using bleach!).
A meat thermometer is perfect for measuring the working temperature of the dye solution. Also, a pair of cheap wood or plastic tongs are handy for handling the canopy while it's in the dye bath.
Fill the container with hot water first, then pour in the dye (this will help avoid splashing dye around). Mix thouroughly but avoid splashing. Remember to use only enough water to fully immerse the canopy. The object is to create as strong a dye solution as possible to speed up the tinting process.
Always test the dye bath using the scraps of plastic remaining after trimming the canopy from its "as shipped" form, principally to determine if the solution is too hot. I've found that an optimal working temperature is 150-160 degrees F, but you should immerse a scrap for a few minutes to determine if there is any chance of deformation at these temperatures.
Place the canopy upside down in the dye bath to avoid trapping air bubbles. To remove any bubbles and to ensure consistant tinting, periodically shake the canopy gently within the dye bath using the tongs. Avoid scuffing the sides of the container with the canopy.
Periodically remove the canopy and observe the level of tinting. Some plastics take dye more readily than others, and the level of tinting you desire may vary, so you have to give it an "eyeball" every few minutes.
If you desire a really opaque level of tint, or if the plastic takes dye slowly, it may be necessary to reheat the dye bath. This is where a stainless steel container comes in handy: remove the canopy, rinse it in tepid water, and set aside. Place the dye container on the range and use LOW heat to gently bring it back up to working temperature, checking with the thermometer. Don't overheat! Then remove from the range, and reimmerse the canopy.
Once the canopy has reached the desired shade of tint, remove from the dye bath and rinse thouroughly with tepid water, then dry using a soft cloth.
Voila! A professionally tinted canopy!
-- Dave Tatosian