Re: I agree with you and support a user option to select pale/bright.
The updated (as of now) brighter colors are not as "poke your eyes out with a rusty nail" bright as they were before (MobiSystems), so personally I don't feel that a "pale / bright" setting is necessary.
And then, as already noted above, the designer did take in the feedback that his initial color choices were too pale and made them brighter.
A happy consensus (on chip colors) then?
1927 Henry Ford: Any customer can have a car painted any color that he wants so long as it is black
2017 MobiSystems: Any customer can choose their preferred color scheme in AquaMail so long as it is pale
One of the most apparent color changes is that of the app's action bar - "overall app color". Used to be a "juicy blue" and now it's a dark cyan.
And even though this has a lot of relevance / importance for the app's branding (that blue app? blue mail, erhm, type mail. the cyan one? aqua, of course!) --
-- that color can still be changed (in app settings -> look and feel) and in 1.8 it can be done in the "light" and the "dark" themes (before, only in the "material" theme).
So personally I don't feel that we're going backwards, quite the opposite.