Diagnosing the Problem. If leaves on an aloe plant develop dark spots, it's critical to diagnose and correct the problem quickly. The most likely cause is too much water, which promotes growth of fungal microorganisms that cause spotting of leaves.
If you're painting Plexiglas, not just any paint will do. Some paint may not adhere well, if at all. Acrylic paints work best on Plexiglas, and spray paints designed for plastic work as well. Clean the Plexiglas with water and a mild soap such as liquid dish soap, rinsing it off thoroughly afterwards. If your goal is for the paint to adhere well, scuff it up with a fine-grit sandpaper; paint doesn't adhere well to slick surfaces, so the sanding gives the paint something to grip.
In some cases, painting of plywood is required or desirable. Top quality acrylic latex paints are the best choice for exterior surfaces. For best performance, use MDO plywood if it is to be painted. Paint on MDO will not fail from checking of the wood or from peeling because of the wide dark bands of summerwood.