A great, complex-appearing border that's built of easy half-square triangles in just two different color pairs! Related corner/border at https://www.pinterest.com/pin/38702878023804504/ More trick patterns at https://www.pinterest.com/yrauntruth/quilt-tricks-hacks/ and https://www.pinterest.com/yrauntruth/quilt-paper-piecing-foundation-piecing/
A variation on the complementary color combination. In this case, you take one primary color and two complementary ones (the colors that lie on both sides of the primary color’s antipode on the color circle). The effect created by such a scheme is just as contrasting as the one before but slightly less intense. If you feel unconfident about using the complementary scheme, use the split complementary instead.