@-sofia- I believe they use paints or dyes that are edible. But I'm not a fan of many wood based toys as they seem to be made of a type of wood that would splinter easily and I don't want a pig getting splinters in their mouth.
I'd either go for a tree branch type wood or even better give them homemade toys. An empty toilet roll with a different hay stuffed in it goes down a treat here. Or a paper hay filled with hay and a few veg pieces.
Most colored chews for small animals claim to use safe and edible dyes but in reality they really are not safe. I would go for natural toys like willow balls, seagrass balls, non colored wood chews, hay mats, cardboard tunnels, etc. Or you could use diy toys like toilet paper rolls (ovs no tp on them, just cardboard)
Or you can just not use toys at all, animals don't understand the concept of toys and those products are mainly directed at the owners for profit rather than pets themselves, piggies would just love if u give them a shaded area or a tunnel made of simple cardboard, or just throw a towel over their C & C cage to make a nice cozy dark space for them to hang out and nap in.