Halo and CWP are what they call tri-coat paints. That is, there's a white base coat, a middle pearl coat, and then the clearcoat. It is notoriously difficult to match 100%.
I have a 3-stage touchup kit from
www.automotivetouchup.com and it does well enough. I generally do the base coat first, and then just mix the pearl and clear together and apply on top.