A color scheme (or colour scheme outside of the U.S.) is the colors and shades of the different faces' stickers, or another form of representing colors, on a twisty puzzle.
For example, the standard Western color scheme on a Rubik's cube has white on the top, yellow on the bottom, orange on the left, red on the right, green on the front, and blue on the back.
Most cubers use the Western color scheme (also known as the BOY color scheme), but many Japanese cubers tend to use the Japanese color scheme instead.
Many cubers who use stickered puzzles create their own color scheme based on the Western color scheme (or, in fewer cases, the Japanese color scheme), but with various shades of the original colors.
Very few use color schemes that don't resemble that of the Western or Japanese Color Schemes. The most famous to not use either of the two is Sarah Strong, who uses her own.