I personally LOVE purple, but I think it is easier to print on white fabric, regular transfer merges well on white, if you print the design on full color, the colors look brighter on a white canvas, also the transfer for black/color shirts is more expensive, the spare zones of transfer sometimes show, and there is also the issue of the shades... it will be hard to find the exact same shade of pink/purple/yellow for every shirt of the staff members, white on the other hand is always white :-)
What could be done is use accessories and other apparel on those colors, like wearing pink pants, purple scarf and yellow Converse shoes for example.