Hi all, 

Used a quality deep purple colour paste to colour my cake mix and it was the desired colour when put in the cake tin, however when baked the cake was two tone, bottom half green, top half blue and marbled between, none of it purple.  Was it the cake mix, I used Wrights Madeira cake mix, it was a large cake and baked for nearly two hours, asked a few other cake makers I know and of them have seen or heard of this.  thank you.