Here is a method for tinting Lexan canopies using Tintex or Ritt fabric dyes.
Before doing anything, get a piece of scrap canopy material
Wipe down the scrap with denatured (99.9% pure) alcohol (otherwise known as methyl hydrate). If this damages the scrap piece in any way, do NOT use this method to clean your actual canopy, use warm water and mild soap instead.
Avoid touching the scrap piece at all. Any oils from your fingers may affect the outcome.
Find a container that is a bit bigger than your canopy, preferably something you don't intend to use again. Stainless steel pots work well here.
Use hot water from the tap, just hot enough that you can't keep you hand in it (55°C/130°F is about right), and fill your container so that it will just cover your canopy by an inch or so.
Add about 1 cup of vinegar for each gallon of water used.
Add the dye. The idea here is to get the strongest solution possible to increase the dye penetration use 2 packs if necessary. To get a smoked tint, use 2 parts black to 1 part royal blue (colours vary).
Place your piece of scrap in the solution and slowly agitate it (this is to keep any dye "clumps" from sitting on your piece and affecting the final shading.
Depending on the desired tint, colour used, material and whether it's Monday or not, it can take anywhere from 30 seconds to 15 minutes to get the right tint.
Remove your piece when the tint is a little darker than desired and rinse with cold water.
Now, if everything went well, repeat these directions using your actual canopy. If the water has cooled, use some hot water to bring it back up to temperature.