Ok firstly this offer only worked for me with the Doughnut colour - i tried with a couple others but no luck, but feel free to fiddle around yourselves.
All colours are half price - but for some reason the second Doughnut colour doesn't seem to add to the total cost (infact it takes 1p off!) see below for instructions. Free click and collect too!
Please follow carefully and don't moan if you don't do it correctly...
Firstly place 2 separate colours in your basket then add 2 of the Doughnut colour (so 4 in basket in total) then remove the 2 you added earlier leaving just the 2 Doughnut colours in your basket - total should be £4.49. I tried a few times and it worked a treat, saved £13.51! Good luck!