Your right, to many colours. Limit yourself to say 3 main colours, for example, Ultramarines are Blue and Gold, Salamanders use Green, Gold and Black, Cimson Fists are Blue, Red and Silver, Hawk Lords are Purple and Gold and Howling Griffons use a Red/Yellow Quartered Pattern. You get the idea, none of these use more than 3 colours. Then you add detail colours such as a Black Bolter Casing, Black Flexible Armour, Bone coloured Parchment on the Purity seals, skin etc. You will end up with a striking colour scheme, your actual model and your painting talents are good, but you really need to redo this using less colours. Also, like the gore on the sword