Crystal When a colour has no effect in or on it, it is the standard version of that colour. Classic Crystal (Foiled) is where the glass is completely colourless and you can see straight through to the silver foiling on the back. The foiling is reflective like the back of a mirror and helps the colour in the glass shine to its fullest potential. Crystal AB 'AB' is short for ‘Aurora Borealis’, also known as the Northern Lights. This effect has an iridescent coating that covers the top of the crystal making it shimmer like the rainbow, predominantly in hues of pink. Please note: the AB effect can look different depending on the brand of crystals.You can find a detailed description of all the Crystal colour effects in our Handy Guide To Crystal Colour Effects blog post.