Rules are made to be broken. Who said curvy women should only stick to black, or that tall girls shouldn't wear heels? Experiment and wear what you feel -- what's important is that you know exactly what looks best on you and what makes you feel good. Fashion has always been about having fun anyway, right?
Having half-hearted recommendations makes you appear as though you don't have a backbone--not a message you want to convey to the world. Declining may not be easy, but it's better than having you look weak. By the same token, a strong, well-crafted testimonial also highlights what you believe is important and positively reflects on your values and credibility.