These are morning glory flowers. Maybe in another color they would be "dodecagons, hexagons, and squares" but you can't fool me. In these beautiful shades they are the morning glories of my childhood memories.
Well you can adopt them if you want. The main dark blue is one of the few colours the synergy group and I agree on: #003399 (a web-safe dark blue which is currently out of the zone where Spoonflower's print profile goes a bit strange). From there it's a bent gradient towards but stopping short of true white #FFFFFF going via #3366CC, #6699FF, #99BBFF and #CCDDFF.