With the population ageing in Taiwan, it is projected that elder care robots incorporating smart technologies will play an essential role in ambient assisted living. This research has two purposes: (1) to investigate whether older adults' colour‐emotion associations and colour preferences for robot appearance affect their perceptual judgements; and (2) to explore gender differences in their judgements. Phase I of this research uses a questionnaire to investigate 91 participants' preferences for robot style and their emotional trigger words for the role of robots. Phase II experiments were performed on another 60 older adults to identify whether their colour‐emotion associations and colour preferences affect their perceptual judgements. The research results show that, regardless of gender difference, participating older adults prefer a robot with non‐human–like features. The results also show that there is no significant difference between males and females in terms of the effect of colour‐emotion association on a robot's appearance. Older adults tend to associate warm colours with emotional semantics, such as friendly, comfortable, reassuring, gentle and lively. Preferred colours include red, white and yellow. Black and grey are almost never preferred by older adults. There are significant differences by gender in the preferences for the colours white and purple. Older females prefer purple more, while white is preferred by older males. For the other colours, there were no significant differences between males and females. Colour attributes do not have any effect on colour‐emotion association, whereas colour preference is highly positively correlated with b*.