Guy,
On the subject of blue:
The particular shade your after is "Bleu Imperial".
I can give you a recipe in oils, perhaps you can find equivalents in acrylics?
Base: equal parts of talens rembrandt Indigo extra + Winsor & Newton Winsor Blue, add very small amounts of titanium white until it looks right... iow, make it a
little lighter so that you have a very dark blue, but still a blue.
1st shadow wet on wet with the base mix without the tit. white.
1st highlight wet on wet with tit. white with some of the base mix, or else cerulean blue, ... even an off-white - fe. tit. white with some earth colour (raw sienna or raw umber) added - will work well...
deepest shadow, wet on
dry, base without tit. white but + some black, sparingly in the "nr. 5" zones acc. to the "stop sign".
lightest highlight, wet on
dry, tit. white with base colour added, or cerulean blue, sparingly on the nr. 1 zones of the "stop sign".
Johan