How to create multiple mesh colors in one package?

Not sure how to word this but How do I create a package on s4s that includes multiple colors of the same mesh, so when I log into the game and select my item its all on one thumbnail? I did merge packages, but all 15 colors of the same skirt appeared separately. for example, when you click a pair of pants and all the colors appear when their swatch is pressed. I researched how but every thing just told me to merge packages...