I suppose, in theory, sustainable fashion shouldn’t have any one look. After all, surely the whole point of prioritising ethics over aesthetics is that clothes design should not be all about what they look like, but about how they are made: the raw materials used, the industrial processes undergone, the people employed, the carbon footprint of transportation. But in reality, it does have a look. You can’t take aesthetics out of fashion. Sustainable fashion has style rules, too. Just different ones.
Some of this is simple practicalities. Sequins, being mostly made from non-biodegradable fabrics, are a no-no on environmental grounds. If you jazz up a T-shirt with decorative zips or emblazon it with beading or glued-on trims, you make it much more difficult for the fabric to be usefully recycled or reused. Therefore, streamlined design is favoured. Textile dyeing is one of the most water-intensive elements of the clothes production cycle, so bright colours can be a red flag.
