Turn a photo black and white while one subject keeps its colour. A single red coat, a bunch of flowers or one bright object stands out against a monochrome frame.
How the color splash effect works
Upload the photo and name the element that should stay in colour, for example 'keep the red umbrella in colour, everything else black and white'. Say how saturated it should be. Run the tool and check the boundary of the coloured element, especially fine edges. If colour bleeds outside it, mention that in a follow-up instruction and run again on the same upload.
Tips for the best results
Pick an element with a distinct colour and clear edges; that is what makes the effect read. Ask for a rich monochrome conversion with real contrast rather than flat grey. Say whether the retained colour should be natural or boosted, and check for fringing along the boundary.