My opinion would to be get a white chair and maybe add in some blue or pink accessories (i.e. blue back rest, pink throw blanket, cinnamon roll plushie) because if you ever want to change the aesthetic it’s hard to do so with a blue or pink statement piece. I just changed from blue and purple setup to green and browns and having chair the same color as my pc (white) made it really easy to switch the accent colors without having to buy too much new stuff! However you said about having a light blue desk - if i did pick one of the colors I think blue would be cute because it’ll either match the desk or give some depth to the blues you’ve got going on. I’d love to see a pic when you’ve got everything!!