Jet black icing is hardest to make.  I learnt the hard way that I could first add cocoa in icing and then very little black would even make jet black icing and let it sit in fridge for a day for color to get more deep.  For red color I mixed Wilton red (no taste) color and red red to make good red icing.  My son was so happy with his Spider man birthday cake and with spider web on the side too.