I love the green coat on Catherine but I think we can see why she chooses the light blues because she is much more visible. When getting out of the car in Blackpool if you had been waiting across the street in the rain for 30 minutes you could've found her hard to spot in the clump of dark colours and brollies.
I personally like her dress uniform. It clearly makes life simple and she is completely modestly covered up so no chance of a cheeky cleavage shot. She can focus on the task at hand, relax and make her day be about the people she is meeting. Perhaps an idea would be for her to ask various designers to come up with versions of The Modest Dress that make it more up to date on cut or colour.
In future years although not the monarch, she will inevitably take many of the roles and tasks of Her Madj. I do think she is building a uniform around her identity so everyone will be able to spot her a mile off, just like the Queen. And when she feels like it she can go glam but a uniform relieves her (and her stylist) from dreaming up a bazillion outfits a year.
So many of us on this thread have been squawking for pantsuits. She has the perfect figure to carry them off and each time she's worn one she looks amazing. So as Curly and so many others have said, she really should add that as a missing uniform element. I wonder if it's purely the palace and the Queen herself dissuading her. As someone up thread quoted her implying she gets a bollocking if her skirts are too short.