I used to think a brunch outfit just meant anything with a floral print and sleeves short enough to show you'd made an effort before midday. What actually sorted it out was realising brunch clothes have one job that nothing else quite has: you're sitting down for two hours, eating something with a sauce, and you need to look like you tried without feeling strapped into anything. The fix wasn't a different print, it was paying attention to how a fabric behaves when you're sat at a table rather than standing in a changing room mirror.
The colours that actually work for this are softer than you'd think a summer occasion calls for. Washed out yellows, pale greens, a proper stone or oat rather than stark white, because white under a cafe awning shows every splash of coffee and every crease from the bus journey there. Stripes work hard here too, especially a wider navy or terracotta stripe on something linen or cotton, because it hides the creasing that comes from sitting rather than pretending the fabric won't crease at all. Where this whole category falls apart is anything that needs ironing to survive the walk there, or anything so fitted through the middle that you spend the whole meal holding your stomach in rather than eating. A structured shirt dress in a stiff cotton looks brilliant on the hanger and is miserable after one bread basket. Equally, anything strapless is a gamble the second you lean forward for the menu, and a jumpsuit with a fiddly button fly is a genuine liability the one time you need the loo before the bill arrives.
What separates a good one from a disappointing one is almost always in the fabric and the seams rather than the print. A linen cotton mix with a bit of give drapes properly over a stomach and a bust instead of clinging and printing every seam line onto your skin by course two. Look at where the side seams sit, whether there's actual ease across the back and the bust rather than just at the hem, and whether buttons are sewn on properly rather than hanging by two threads after a single wear. A co-ord with a proper weight to the fabric, something with a bit of drop to it, moves and sits better across a chair than anything papery and light that was clearly chosen for how it photographs flat on a hanger rather than how it survives sitting still for ninety minutes.
Get the fabric and the fit through the middle right and the rest of it looks after itself, whatever colour or print you end up reaching for.