The chakras are commonly presented with a rainbow sequence running from red at the base to violet at the crown. That arrangement is recent, and the older sources describe something else.
Traditional colours follow ritual logic
Tantric texts assign colours to internal centres, but the assignments vary between sources and do not form a spectrum. A centre may be described as smoke-coloured, white, golden or dark.
The choices follow the elements, deities and syllables associated with each centre in a given practice. Colour is one attribute among several used to construct a visualisation accurately.
Because different lineages use different associations, the colours differ correspondingly. There was no reason for them to agree, since each set served a particular ritual sequence.
The rainbow ordering came from elsewhere
Arranging the centres along the visible spectrum requires the spectrum as an organising idea, which belongs to a later European scientific vocabulary rather than to tantric literature.
The mapping spread through theosophical and early twentieth-century esoteric writing, which combined Indian material with Western occult systems and a growing interest in light and vibration.
Once printed in accessible books, the scheme was copied repeatedly, and the neatness of the ordering helped it displace the more variable traditional assignments.
Neatness explains much of its success
A sequence that runs cleanly from one end of the spectrum to the other is easy to remember, easy to illustrate and easy to teach in a single diagram.
It also supports commerce, since coloured objects, cloths and printed charts can be produced against a fixed and universally recognised scheme.
Variable traditional colours offer none of those advantages, which is a plausible reason the standardised version dominates popular material.
The addition brought other associations with it
Alongside colour, the modern scheme attached each centre to a psychological theme, a developmental stage and sometimes an endocrine gland.
This produced a ladder running from survival concerns at the base to transcendence at the top, a shape that reflects twentieth-century developmental psychology more than the source texts.
The composite is internally consistent and widely used, but it should be described as a modern synthesis rather than as ancient teaching.
Knowing the history changes how the scheme is used
Treating the colour sequence as a recent convention makes it easier to use as a memory aid without asserting that it was handed down unchanged.
It also clarifies why older sources appear to contradict popular charts, since the two are answering different questions in different periods.
None of this settles the value of the practices themselves, which are assessed within the traditions that transmit them rather than by the accuracy of a colour chart.