Here is a tricky question, so I will explain it as a working example.

A particular t-shirt can come in different colours (red, blue, green) and different sizes (small, medium, large)

I have created the option names (colour, size) and I have created the option values for these names (red, blue and green for colour) and (small, medium and large) for size.

How can I set it so that if a customer chooses a particular colour (let's say red), they can only choose "small" and "medium" , but "large" is not availaible ?

Kind regards,
Anthony