Apply Discount to Product Variant

Is there any way to apply a discount to a selection of variants within a product, rather than to the product as a whole?

I have my colour range set up as an option in a main product, and that option contains 11 variants. I would like to offer a sale to my customers of 20% off our new colours, which is 5 of those variants.

I can figure out how to apply a discount to a product, but this puts the whole colour range on sale. I can't enter a negative value for the variant's price to reduce the price when the sale colours are selected either.

How do I do this? Would like to run the sale tomorrow, so a quick response would be very much appreciated.

It's very disappointing that Hikashop requires professional development to do such a simple action. I have neither the time nor the money to hire a coder just to be able to put 5 things on sale.