What is the recommended paint brand and color for a light blue backdrop?
Whatever inexpensive latex paint your local Big Box store sells, assuming that you're painting a wall blue.
If you're painting something else (Masonite, linoleum, aluminum flashing...) ask the store's paint guru for advice.
Chuck
I use Vallejo Acrylics Sky Blue from their Model Air line and a color called linen white (latex wall paint) from Home Depot. My backdrops are 1/8" hardboard. I give them two coats of the linen white and let it dry. Then, starting at the top, I airbrush on the sky blue, gradually applying less paint as I near the horizon. This has the same effect as what ndbprr does, almost white at the horizon blending to almost blue at the top.
Connecticut Valley Railroad A Branch of the New York, New Haven, and Hartford
"If you think you can do a thing or think you can't do a thing, you're right." -- Henry Ford
I bought quarts of a sky blue (Behr P510-5 Perfect Sky) and white at HD. I used 4 mini tray / roller sets and mixed variations and applied as described above, using the 4 separate rollers to make bands that I blended one to the next. This was done on the garage floor on the masonite background. I actually did it twice, as the first time I added some clouds, a poor first attempt that needed a re-do. My background is not very high as I wanted the ability to reach over it (layout is a bit "too wide").
I'll find a photo:
Paul
Modeling HO with a transition era UP bent