Magento Magmi如何添加自定义选项彩色图像

I am using magmi for product and product custom option import

For custom option I am trying create size and color its created successfully through below CSV

sku,name,description,price,Size:drop_down:1,Color:drop_down:1
E90451,T-Shirt,A T-Shirt,5,Small|Medium|Large,red|green

Now, my issue is I need color with image like for red (red color image) and for green(green color image), and I'm not sure how to do it.