I used Red-orange the red orange color at the end of the word "Complementary" (find it on the color wheel and go directly opposite to the blue-green) Blue and Green which are on each side of Blue-Green.
A Split Complementary Color Scheme is made up of three hues. First you choose your main starting color and select the two colors on either side of its Complementary color, which is what I did.
You can see that no matter where you start, there will always be at least one Tertiary color in your selection. Tertiary colors are blends and will make your resulting palette quite sophisticated with an infinite number of subtle mixtures. This color scheme is extremely popular with artists and designers. Lots of other information at Color Wheel Artist.