Dorothy and the Wizard appears to be in the order of Transformation, Purple Orange Green Red Blue Yellow

Each colored circle is surrounded by six more colored circles which are each surrounded by six more and so on, an on etc. One can only see seven at a time. Then as the person concentratively meditates on one of the six surrounding circles it becomes invisible and the person enters into the relationship defined by that invisible circle.
In the case of the suns over Mangaboo, the invisible sun would be the green one. That indicates an entry into perception or the lack of perception, empathy (in this case the lack of it) and the world of vegetation.
Lights combine additively and pigments subtractively. Yellow and blue combining to make green on Dorothy's face would indicate that the light was negative light, that is, the specific absence of light. Virtual light. In other words, that they were seeing by a sort of colored darkness.

In the context of Green then, the following is a secondary sequence of Transformation.

Green / Clear - (awareness of transition) passing the suns of heatless, virtual light - parallels - being aware that a certain position of equilibrium has been tentatively and tremuloously reached. Entry into the green realm of awareness of the process of thinking.

Green / Purple - (awareness of void) discovery that one can walk on air - parallels - discovery that virtual perception is not dependant on immediate causality but is defined by absence rather than presence.

Green / Orange - (awareness of rock / response) trial about rocks and arrival of wizard - parallels - thoughts demand to be dealt with and if equilibrium is maintained eventually quiet down.

Green / Green - (awareness of awareness) predictions vindicated - parallels - thoughts are adaptable to any interpretation as long as they receive the attention that they demand.

Green / Red - (awareness of conflict) contest between wizard and sorcerer - parallels - conflict between deception and actuality. In this conflict deception and emptiness wins. Decisive division of concept a major factor.

Green / Blue - (awareness of judgment) the royal bush - parallels - allowing judgment to judge itself. One directs judgment by influence rather than by force.

Green / Yellow - (awareness of limits) escape to the black pit - parallels - awareness that allowing judgment to judge itself has immediate limitations and is not actually acceptable when dealing with anything more complex than obvious immediate cause and effect.