Change the background colour of a photo

A background colour works when it separates from the subject in brightness. Dark hair and a dark suit disappear into navy and stand out against pale grey, sand or sky blue. A light product needs the opposite. Saturated colours pull attention away from a face, so for portraits muted tones are the safer choice and vivid ones are better kept for objects and for social posts that are meant to shout.

For anything that sits on a website or in a presentation, start from the colours already there. Take the exact hex value of the brand colour, or of the page background, and enter it in the picker. The picture then belongs to the layout instead of sitting on top of it.

Light bounces. A person photographed in front of a green hedge has a faint green rim along the shoulders and in the hair, and someone standing by a red wall is slightly red on that side. Removing the background does not remove this spill, because it is recorded in the subject's own pixels, and the tool does not recolour the subject.

Put a strongly different colour behind such a cut-out and the rim becomes visible. You have two ways round it. Choose a new colour from the same family as the old background, where the spill reads as natural light. Or use a neutral, such as white, grey or black, against which a faint tint is hard to notice.

The commonest practical use is making a set of pictures match. Staff photos taken on different days, in different rooms, by different phones look like a collection of strangers on an About page. Put all of them in one batch, choose a single colour, and each face lands on an identical background. It is the cheapest way to make a team page look planned. Crop them to the same shape afterwards with the crop tool, and the set is done.