In this first stage, having taken note of the various tones, I then identify the warmer and cooler hues, dividing the painting up into masses or blocks of warm or cool colours. In this case, the cooler leaning toward cool reds, violets and blues, the warm towards the yellows.
In landscapes involving a lot of green, underlay  shades of reds, yellows, violets and or ochre make for a richer, more  luminous and interesting mass of colour once the green is laid on top. The cold sky has an underlay of a relatively cool pink-rose madder.

In this second stage, still dealing with colour mass, the cool-pink sky now has an overlay of  ultramarine mixed with white, leaving enough of the cool pink showing through and around it to make it less "flat colour" more light-filled.
The (palette-mixed) green of the grassy foreground has been added, but still allows the base notes to show through, describing the areas in shade or sunlight and also retaining the various nuances of  the green grass itself. The typical silvery green of  olive trees in the mid distance has been achieved with an overlay of viridian green, lightened in tone with white, but again with enough of the under colour, in this case magenta, showing through. This helps them "recede " into the distance but also mingle with the sky tone and "feather" a bit at the tops. The deep purple of the olives in the foreground has been overlaid with a darker viridian.

The third and final picture shows a number of changes;
A lightening up of the dark tones in the foreground with strokes of a mix of warm greens and ochre to bring forward the nearest olive trees.
An overlay of ochre and green on the dark trunks.
A slight warming up of the tops of the far olive trees with some cool yellow mixed in.
A pushing back of the brighter area of grass under the distant olives using an overlay of violet to mute the bright yellow-greens.
Strokes of ochre mingled into the foreground.
This creates the final composite colours desired.