Now I know what you're thinking. Square colors don't exist. You can't have a noun modify another noun!!
WELL YOU ARE ALL WRONG. WATCH THIS:
What do Red, Yellow/Orange, Green, and Blue make? SQUARE COLORS.
To me, this kind of color scheme evokes memories of graham crackers and crayons. Brightly organized notebooks. Acrylic paints. These colors are essentially two sets of complimentary colors all paired up in a nice bright harmony that just draws super attention to itself, creating both complimentary and more analogous pairings all at once. Use at your own risk - this set is bound to draw some eyes!
You can definitely play up this scheme by using one or two colors as bold mains and backing up with the other two - can you imagine bright red hair, yellow orange dress, green shoes, and blue nail polish? Google couldn't, but I CAN.
Get creative! What other organizations of this scheme would scream AMAZING?
Next week: THE FINAL INSTALLMENT: Tetrad Colors!