Beige sandals are the ones you reach for when you can't decide what else to wear, which is really the whole point of them. They sit under a hemline without arguing with it, they don't pull focus from a print, and they do the job of a neutral shoe without going anywhere near trainer-white or safe black. If you want one pair of warm weather sandals that goes under most things in your rail without a second thought, this is the colour that tends to manage it.
Where they let you down is anything formal in a cool light. Beige can look slightly flat under office lighting or against a smart navy dress, it wants daylight and skin and a bit of tan to look deliberate rather than accidental, so for a wedding or anything with a strict dress code I'd still reach for something with more shine or a proper heel. They also show every mark going, scuffed suede or pale leather at the toe looks tired fast, and a day of pavement walking in a city will tell on them by the second wear if you don't take care of them. Wipe leather ones down after a dusty day, let suede ones breathe rather than cramming them straight back in a bag, and keep a small suede brush somewhere you'll actually use it. Over a summer they soften and mould to your foot in a way that's genuinely nice, but they also pick up the shape of your foot permanently, so buying them half a size tight hoping they'll stretch is a losing game, they stretch but they stretch into the wrong shape. On fit, go with what you'd normally take and check the strap sits where your foot actually bends, not half an inch in front of it, because that's what causes rubbing on the top of the foot by mid afternoon. If there's an ankle strap, it should sit with a finger's width of ease, not pressing a line into your skin by the time you sit down for lunch.
On shade, I've had more luck with a sandal that leans slightly warm, closer to sand than to grey putty, because it reads as a colour choice rather than an accident next to most skin tones. A toasted or caramel beige works through spring into early autumn in a way that a cooler, greyer beige can look a bit like it's trying too hard to match everything and ending up matching nothing. Stick to one pair that does most of your summer and let the rest of your shoes be the interesting ones.
Let them dry away from direct heat after they've been wet, radiators and strong sun both crack leather faster than normal wear ever will.