You can spot a good pair of blue shorts from the other side of a room, and it's not about the cut, it's the colour. A proper denim or cobalt holds its tone under any light, while the bad ones go either chalky or slightly greenish by mid afternoon, especially under shop lighting that flatters nothing. Hold the fabric up to a window before you buy. If the blue looks like it's fighting the daylight, it'll look worse on you at a barbecue in July.
The easiest shades to live with aren't the loud ones, whatever the mannequins suggest. A mid denim blue or a faded, worn in indigo goes with almost everything you already own, which matters more than it sounds because most of us aren't building a new wardrobe around one pair of shorts. Navy is the quiet alternative if you want something that reads as neutral rather than seasonal, and it's the one I'd reach for with a plain white top and no further thought required. Pair blue shorts with stripes and you've accidentally dressed like you're on a boat, which isn't always a bad thing, just know it's happening. A linen shirt left open over a vest, a simple sandal, a soft cardigan on the cooler evenings, that's the whole outfit sorted without trying. Tailored blazers work too, oddly, if you want something that looks like you made an effort when you didn't.
If you've got none, start with a mid wash denim short in a straight or slightly relaxed cut rather than anything too fitted or too frayed. The fitted ones look lovely on a hanger and then dig in the second you sit down for a long lunch, and the deliberately distressed ones have a way of fraying further than intended after one wash, leaving you with something that looks less lived in and more lived through. A straight leg forgives a multitude of sins and still looks put together.
These earn their keep from late spring through early autumn, for the obvious reasons, but they're also quietly good for anything that isn't formal. Weekend markets, long pub lunches, the school run on a hot day, a weekend away where you can't be bothered packing for three different occasions. They don't do well for anything that needs you to look especially polished, so don't fight them into that role.
Tomorrow I'd put mine with a plain white tee, flat sandals, and nothing else to think about.