Answer: The best protection against sunburn is a healthy canopy of foliage on the pepper plants. If disease, insect damage or poor nutrition are causing the plants to have a rather thin, spindly canopies of leaves, the best approach is to first remedy those problems.
If you need to use a shade, select as light a shade as you can as good sunlight is important for the growing plants. Most shade materials come in white, black or green, and a few in brown. Any of these would be fine as color need not be a factor in selecting one.
A lightweight row cover such as is used for seed starting or insect exclusion is one option. If you use a black shade fabric select one with no more than 25-30% shading, and position it well above the plant's foliage to allow lots of reflected light in from the sides.
Thanks and good luck with those peppers!
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