Based on your current specifications, I would probably go with something like:
PRODUCTS
productID, productName, productDescription, productPrice...
PRODUCTOPTIONS
prodOptID, ProductID, SizeID, ColorID, SKU
OPTIONCOLOR
ColorID, ColorName
OPTIONSIZE
SizeID, sizeName, addPrice
Where addPrice is the additional price for that size option, which would be added to the productPrice for the total.