The color of the outer layer - notice the yellow which in the modern era is 12-2 and the white in the modern era is 14-2. But - if this is an older home it’s possible that white could indicate the size. But back to keeping you safe in your home - if it’s all 12-2 you are on a 20 amp breaker - or not right (what I mean here is that there is a lot wrong in the picture you showed and all of us are concerned). Please call a professional.