The techniques I use to make fairy wings that appear to glow in different colors.
On a dark or black background, after you've drawn (or made an outline of) the fairy or character that will have wings - use the fill tool at approximately 50% (depending on the color) to create the main form of the wings. To make changes to the shape afterward, copy the color, and then use the line or draw tool at 100%.
Draw the veins as very thin lines in a light color at about 40% transparency. Don't make too many. Using the airbrush tool at about 45% with medium width spray - trace over each vein with only one layer. This will soften the look of the veins and you'll start to see a glow effect.
Now you can chose the colors you want to use for the wings to appear iridescent. I don't like using more than three colors, or they will mix and look too muddled. Bright pastels are the best for showing up.
Use the airbrush tool at about 40% to 50% transparency to put the colors on in any pattern you like. It can be dots, lines, squiggles or any other way you choose.
The finishing touch is a glow on the outside edge of the wings. Chose a color that seems to fit what you've used so far; then with the airbrush tool - set at full width and about 40% transparency, trace as close to the outer edge of the wings as possible. Try to do this all in one stroke, since the color gets too intense if it overlaps. You can see that depending on the colors you chose, you may have very bright wings or a more muted tone. I hope this helps you. ;)