You can paint them but painting the awnings will cause them to lose their translucency. If the panels are in good condition, you can hose off the accumulated dust and dirt. If the dirt is caked on, you may have to use a pressure washer. You should hose down the panels periodically to prevent dirt from accumulating.
If you decide to wash the awnings, don't use a detergent, which may contain ammonia or chlorine. This may cause the awnings to become yellow. Instead, use a mild nonabrasive soap.
When the panels have weathered extensively and fibers appear on their surface, you may want to take additional measures. The exposed fibers entrap dirt particles that contribute to further deterioration and reduce light transmission.
You can paint them or stencil them. Use Camp dry after you are finished to keep the awnings dry. They use that on Tents and can be bought at a sporting goods store.