Create products with color variants
You have Table called 'product'
To find out the unique product among the one product, u need to maintain these structure.
1.Product table
2.Characteristics table. EX(size, color etc)
3.Product_Price table (A product price may vary based on characteristics. EX: Pendrive is a product. But their characteristics may change the price. 2GB pendrive,, 4GB Pendrive, 8GB pendrive. So, Based on characteristics the price also varying. This table for that purpose)
4. Product_Characteristics table. This is need to map the product and characteristics. Primary key from product table and primary key from characteristics table.

Then you can get one valuable structure for eCommerce products.
For stock you have to maintain from product price table.