Yesterday I spoke with someone who has colored aluminum roller shutters. He called the color brown-gray and there are no problems at all. No warping or sticking on hot/cold days. Full sunlight does not affect the function at all. And we had enough hot days this summer. I believe it is a matter of taste and budget when someone chooses colored aluminum roller shutters.
Last week had a conversation with the roller shutter builder. The statement was essentially that they only make roller shutters >220 cm wide in aluminum anymore, because plastic will warp inward or outward. Not immediately but eventually, and you want to enjoy your shading for a long time. I am looking forward to the offer with the aluminum shutters.