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The 80mm f/11.25 won't show much colour, by virtue of geometry (it's well within the Fraunhofer criterion). The 90mm f/10 on the other hand needs colour corrected optics in order to be achromatic.
Regarding DSOs in small scopes, while more aperture will obviously show you more it isn't true that you'll only see naked-eye DSOs in an 80mm refractor. My 80mm f/7 ED shows plenty more than that, including all Messier objects and then some. An 80mm lens collects a lot more light than a 7mm pupil.
Cheers
Steffen.
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