As a derivative of chocolate, white chocolate consists of milk, sugar, cocoa butter, salt and solids. It has an ivory or pale yellow appearance.
White chocolate is chocolate that does not contain non-fat cocoa solids.
This is the primary nutritional constituent of chocolate liquor—chocolate in its raw, unsweetened form.

So can guinea pigs eat white chocolate at all?
Unfortunately they cant at all.
Firstly, it is far too sweet for them and they just can’t handle that much sugar in their systems.
Secondly, they are unable to eat any kind of dairy product.
So it is a snack that is worth keeping to yourself, and well away from your guinea pigs.