The most common and most likely answer to this crossword clue is the 6 letter word OCELLI
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The straight part
We know that "colourful spots" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case colourful spots = ocelli.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does OCELLI mean?
OCELLI noun- A simple eye consisting of a single lens and a small number of sensory cells.
- An eyelike marking in the form of a spot or ring of colour, as on the wing of a butterfly or the tail of a peacock.