good grief, do NOT buy a mat based on the color...buy it for the value...JT mats are of NO value! They will dull your blades so fast you will go broke replacing them...they are also known for being slick and causing slippage when you cut!
OLFA is the best mat.
The other ones to stay away from are the WHITE rubbery kind you always see at the quilt shows! They do not hold up to a lot of cutting!