Step 1: Post 1 item from your shop which is the same color as the item posted from the shop above.
Step 2: Post a new item of a different color.
Example
Shop A: Green, Blue
Shop B: Blue, Red
Shop C: Red, Yellow
Lets started of with:
Pink
https://www.etsy.com/listing/119753900/embossed-keep-calm-marry-on-wedding
Blue
https://www.etsy.com/listing/113545066/handmade-mulberry-paper-baby-boy-new