Product variations are easy to do. But there are a few steps to doing it.
Go to Products, select Attributes
Create an attribute - "Colour", then save
Select "Configure Terms" - create individual colours (red, green, etc)
Now go and edit your individual product page
Make sure you select VARIABLE PRODUCT rather than simple product.
Select the Product Data section
Select the Attributes section
Beside the ADD ATTRIBUTE button you should see the Attributes you set up in the previous steps. Select it and then click Add
Now click SELECT ALL to bring up the individual attributes you created in the first section. Edit any you don't want to show up.
IMPORTANT: select USE FOR VARIATIONS box (I don't use the show on product page, this only adds the text to the additional tabs section)
CLICK SAVE ATTRIBUTES (don't miss this step)
Still in the Product Data section, select Variations section
Create your variation(s) - you have to include a price here for each variation or no price will show up.
Note: if your products are set to private rather than public, they won't show up in the shop.
Tip: if you want an add-to-cart button to show up with a price, make sure to set a DEFAULT VARIATION selection (this is the DEFAULT SELECTIONS found at the bottom of this variations section). Your customer will still be able to select another variation, but at least they won't be mystified about the lack of a cart button or price. I just discovered this after months of working with WooCommerce.
This works. Swatches and Variations Plugin also works, I use it and recommend it.