Why very young shrimplets all look the same
A young cherry shrimp cannot be sexed reliably in its first weeks, because males and females share the same tiny, translucent juvenile shape before their adult body forms emerge. Both sexes graze, moult, and grow through that stage looking nearly identical, apart from small colour differences that owe as much to feeding and mood as to sex. Guessing at that age produces records you later have to undo, so experienced keepers wait until the batch is well grown and individuals can be compared side by side. The differences, when they arrive, are consistent enough that a patient keeper can sort a colony with reasonable confidence.
Body shape is the most reliable clue
Body shape separates a young cherry shrimp female from a male more reliably than any other sign. The female's body deepens as she matures, with a rounded, curved underside built to shelter a cluster of eggs beneath her tail, giving her a plumper side profile. The male stays narrow and straight-backed, with a thinner tail section and a generally smaller, sleeker build even at the same age. Compare several shrimp of similar size on the same leaf or glass, because shape differences stand out in a group while a lone shrimp can mislead. A shrimp that looks in between may simply need another moult or two before its shape declares itself.
Colour and the saddle as supporting signs
Colour supports the shape reading in a young cherry shrimp without deciding it alone. Females usually carry deeper, more solid red coverage, while males show patchier, paler colour with more translucency along the body. A maturing female may also show the saddle, a pale or yellowish patch visible behind her head through the shell, which is the developing egg mass and confirms both her sex and her maturity. Absence of a saddle does not make a shrimp male, since a young female may not show one yet. Use colour and saddle together with the deeper female body shape for a judgement you can trust.
Behaviour and size in the colony
Behaviour adds a final layer when sexing a young cherry shrimp group. Males roam more restlessly, swimming laps of the tank especially when a female has recently moulted, while females spend longer settled and grazing in one place. Adult females also finish noticeably larger than males raised alongside them, so the biggest, deepest-bodied shrimp in a mature batch are almost always female. None of these clues should stand alone, because a hungry male grazes quietly and a young female swims when disturbed. Read shape first, then colour, saddle, size, and behaviour as a combined picture before you record a result.
Recording who is who once you know
Once a young cherry shrimp is identified, writing it down prevents the same shrimp being re-judged every time the colony is cleaned or moved. A simple per-shrimp note — sex, depth of colour, and whether a saddle is present — helps when you later choose breeding groups, share shrimp with another keeper, or explain a colony's mix. It also stops a pale male being mistaken for a poor-quality female during a sort. Keeping each identified shrimp's details on KinsLe through Pet Pass gives you a clear ID record with owner contact information ready to show whenever it is needed.