Sri Aurobindo
Letters of Sri Aurobindo
Volume III - Part 2
The rays which you saw the trees giving out are there always, only they are veiled to the ordinary material vision. I said the blue and gold together indicated the combined presence of Krishna and Durga-Mahakali; but gold and yellow have different significances. Yellow in the indication of forces signifies the thinking mind, buddhi, and the pink (modified here into a light vermilion) is a psychic colour; the combination probably meant the psychic in the mental.
In interpreting these phenomena you must remember that all depends on the order of things which the colours indicate in 
any particular case. There is an order of significances in which they indicate various psychological dynamisms, e.g., faith, love, protection, etc. There is another order of significances in which they indicate the aura or the activity of divine beings, Krishna, Mahakali, Radha or else of other superhuman beings; there is another in which they indicate the aura around objects or living persons – and that does not exhaust the list of possibilities. A certain knowledge, experiences, growing intuition are necessary to perceive in each case the true significance. Observation and exact description are also very necessary; for sometimes people say, for instance, yellow when they mean gold or vice versa; there are besides different possible meanings for different shades of the same colour. Again, if you see colour near or round a person or by looking at him or her, it does not necessarily indicate that person’s aura; it may be something else near him or around him. In some cases it may have nothing to do with the person or object you look at, which may serve merely the purpose of a background or a point of concentration – as when you see colours on a wall or by looking at a bright object.