Pthalo Blue is a synthetic pigment (full name Pthalocyanine). It is a bright, high instensity blue colour used in oil and acrylic based artist's paints, and in other applications. See (Pthalocyanine) for more details.
Painting 2: the background is dark pthaloblue, and the woman form is done in lighter pthaloblue, turquoise and white.
Then the whole window is glazed with a light blue glaze, which gives the whole thing a sort of greenish glow.
Painting 4: the background is medium pthalo green, and the woman form is done in darker tones of the same green, so the whole form seems to just barely emerge from the background.
Depending on which blues you have in acrylics I would try this with a phthalo blue and a touch of violet or crimson, or Ultramarine.
I suspect you might have balanced them a little too much, just a little BU into the blue will give a good dark which is still definitely blue and not grey, but I think you'll like the mix of Payne's Grey better.
The next day, under daylight illumination, the blues in the shadow areas of the waterfall are way too chromatic...more than they looked when I painted it.