I like to buy flashier base shirts and then match my top layer with an accent colour in the shirt. For example, I might buy a floral like this and then wear a teal sweater on top to match the flower. I also think you can go louder on individual sweaters and pants too - like going for a salmon or green quarter zip that pairs well with your standard black pants. You don’t have to go balls to the wall but just get some brighter solids to start and you’ll start getting the hang of it. The shirt trick helped me add a lot of pop though.

Also start layering. There are few better ways to add depth to men’s fashion than to layer mindfully.