Listen to your gut if you look best in blues stick with it. I don't think the model looks that gorgeous in the colours of the dress so it won't work for everyone.
On the other hands I often order excess items from Boden and they refund very quickly. For example I ordered last wed, received package on Friday, mailed back on Mon -- credited back to my account on Thursday. So I order and try on tons.
I also keep notes on my sizes and wait for sales; but I recall last winter they may have had 30% off limited edition right before the sale and several items were cheaper with the discount than the sale price.