This pic shows you the three most common corn morphs. The red coloured one is a normal. He is dark like that because he is in a shed. The red and white one is an Amelanistic, which means lacking black pigment. The black and white one an Anerythristic, which mean lacking red pigment. The white and yellow one is a snow and it is lacking both red and black pigment. Corns have three main colours; red, black and yellow.
If the pet store doesn’t even know the basic name for the animals they are selling I would avoid buying from them. Any corns snake book is full of pics and names of the most basic corn morphs.
Hope this helped,
Trevor
PS
There are also anerys het for lavender for sale on this site.