Assisting with colours to let the speaker know how long he has to speak.

Hi @AnneBingham! Welcome to the Zoom community, we're happy that you're here 😊

There is no visual way to indicate how much time is left for the speaker. You can try the Timer Zoom App, which features a countdown animation and alarm signal that indicates when time is up: https://marketplace.zoom.us/apps/cXw5IXmqT6SIIBQxgM_PfQ

If this helps, don't forget to click the Accept as Solution button below!