Doogs,
There's a danger in taking a model or profile and then being dogmatic about the accuracy of the colors used to render the scheme. Unless you know precisely the paint the modeller started with, and how much weathering, fading, shadowing, etc, they did; it's impossible to do much other than guess. As an example, the HS site showing Roy Sutherland's HF VII model doesn't say what paint he used to achieve his interpretation of the underside color. Yes, it appears dark on my monitor, but that doesn't mean he didn't use MM PRU Blue, or Gunze PRU Blue or some other manufacturer or some other color. (It doesn't look like glossy sea blue to me.)
This photo below, copied over from Britmodeller, seems to be the most commonly shared photo (only one I've found to download) that's of a high enough quality to show detail. All the experts agree it's Sea Grey Medium over PRU Blue with black/white stripes and Sky codes. Yet the photo clearly shows everything dark simply because of the film quality.
This next image is of a few recent builds to highlight the differences in colors.
The Hurricane I on the upper left is painted Sky Blue which is a very pale blue (Pollyscale 505248). The Hurricane IIb just below and left of it is painted MM Azure before I learned it should be more purple. The Spitfire Vb to the right and below is painted MM Azure with a few drops of deep red added. It's very subtle in difference. The Spitfire PR XI in the middle is overall PRU Blue (MM 2061) and the PR XIX below and right of it is in the High Altitude Scheme of MSG/PRU Blue (Humbrol 144). As a comparison, because you mentioned Glossy Sea Blue, I stuck the Bearcat in the photo.
The lighting is natural and indirect on a sunny day.
This next photo is of the two Azure birds overlapped for comparison:
Even on my monitor the difference is almost negligible. In the plastic it's more obvious, but again very subtle.
While I didn't take a photo, the two PR Spitfires with different PRU Blues (MM and Humbrol) are identical in color, so this next photo is of the PR XI next to my color chips:
This came out dark, but I think I may have cast a shadow as I was taking the picture. The point is that MM PRU Blue is nearly identical to the chip, for all intents to my eye, they are identical. Of note, when I compare the two PR Spitfires, the PR XIX in the HAS actually appears to have a darker blue underside, probably due to the lighter upper surfaces.
Your Spitfire is looking very nice, and if I had the space, time and dollars I'd probably go for larger scales. I'm building a collection of Spitfires that's already over 50, of which about half are completed. So my scale of choice is 72nd.
Tim