please can anybody tell me how to get a nice bright royal blue icing? mine always comes out sea or aqua blue shade, even when i use the wilton royal blue paste colouring.

maybe try a bit of orange to try to cancel out the other greenish undertone. I am trying to think of the same concept with adding purple to icing that is yellow to get it more white. I hope that makes sense. If not maybe switch brands and use amricolor or maybe you aren't adding enough of the blue. Of course let it sit and see if it darkens to the color.