What's the Best Chalk Color for Outdoor Projects?
“Choose your marking chalk color based on two things,” says Lisa Hunter of Irwin Tools. “First, think about what sort of permanency you need. How long will the chalk lines be exposed to the elements? Second, decide what color will give the best contrast on the surface.”
Marking chalk permanency ratings run on a scale of 0 to 4 (look for the rating on the chalk container). Carpenters who work on a variety of projects generally carry two colors—red and blue—in separate chalk boxes. (It’s a bad idea to mix chalks.) They use blue when they need a chalk line that will disappear, such as when they’re shingling. The blue chalk will wash right off after the first rain. Red, on the other hand, is pretty permanent. Use it on a roof and it might take years for it to disappear. But if you’re laying out walls and you want the lines to stay there even if it rains, red is the way to go.
Indoors, if you’re snapping lines on a blue painted wall, consider using violet or white chalk. The chalk will stand out and then dust right off the wall with no residue.