When you export a selection of different coloured garments to your store, we will automatically create mockups for all positions in the first colour, but you will only find the front of the garment is automatically created for all the other colour variants.
The example from Shopify below shows the front and back for the Ash Grey colour, but only the front for the yellow.
Most of the e-commerce platforms will allow you to manually add other images for each of the colour variants you wish to sell. You can do this by manually creating mockups from your products in your GoCustom account. Here is how to download mockups in any colour you choose.