Generally speaking, female Common darters (Sympetrum striolatum) are yellow and males are red. However, as with so many things, the reality is not so black and white – or, rather, yellow and red.

Immature Common darters are usually yellow in colour, regardless of sex; and, as they age, the colours of both sexes often become dull, the males losing their vibrancy and looking quite brownish, the females turning reddish so they resemble males.