pale pink sponge- how much food colour?

[showerhead]

could someone have a look at the second pic on this blog and tell me how much food colouring you'd need to get that effect. I know it will depend on size of cake and make of colour used but will it look paler or darker after cooking? thanks.

doh! forgot to link the pics, but realise i just need to add red drop by drop, just getting in late night panic for no reason. I know what i'm doing now and can't wait to make the cake!