Yellow is the thinking mind. It is a colour corresponding to the main forces of the mind. The shades indicate different intensities of mental light.

The intellect in most men is extremely imperfect, ill-trained, half-developed, therefore in most the conclusions of the intellect are hasty, ill-founded and erroneous or, if right, right more by chance than by merit or right working. The conclusions are formed without knowing the facts or the correct or sufficient data, merely by a rapid inference and the process by which it comes from the premisses to the conclusions is usually illogical or faulty, the process being unsound by which the conclusion is arrived at, the conclusion is also likely to be fallacious. At the same time the intellect is usually arrogant and presumptuous, confidently asserting its imperfect conclusions as the truth and setting down as mistaken, stupid or foolish those who differ from them. Even when fully trained and developed, the intellect cannot arrive at absolute certitude or complete truth, but it can arrive at one aspect or side of it and make a reasonable or probable affirmation; but untrained, it is quite insufficient instrument, at once hasty and peremptory and unsafe and unreliable.