First of all—and this is easy to overlook; I often make the l-to-r mistake when I forget to pay attention to what I’m doing—READ ROW INSTRUCTIONS LEFT-TO-RIGHT ON EVEN ROWS, RIGHT-TO-LEFT ON ODD ROWS.
These colors usually appear only on three-layer warp (3LW) patterns:
Red = UNDER
Blue = OVER
White or Gray = PLAIN weave
Green = optional Under
Light Blue = optional Over — not used very often
Here are some examples: