Ah Grey Knights, where three different kits will make your whole army haha So what exactly are you trying to do? Find a way to use all the bits in the box rather than make some Knights permanently use a certain weapon? Really, Grey Knights will do anything you want them to do and more. You can play medium point lists and literally have a dozen models on the table, and you'll still be likely to win. Were you thinking of normal Grey Knight colors or a unique palette?