Yeah this what I have been thinking for a while now. The Hawaiian Islands are nicknamed by color. The island that we start on is known as Yellow Island. This is why some of the character are also wearing yellow. Yellow is also the color of flower they use to make lais and other decorations with. Melemele means yellow, so it isn't the national Dex.
The top right Island would be Pink Island. `Âkala Island
The biggest Island is Red Island. `Ula`ula Island
And the one on the far left is Purple Island. Poni Island
They might change the colors, but I am doubting they will with how close they have stuck to the real life counterparts. Although they may use Red, Blue, Yellow and Green.