Colours give clues about their distance. For example, the bluest galaxies are relatively close, while redder galaxies are further away.

Let us examine an image of galaxies accordingly and make sense of their distances from their colours.

Image description:

A galaxy field on the black background of space. In the centre, stretching from left to right, is a collection of dozens of yellowish spiral and elliptical galaxies that form a galaxy cluster in the foreground. Among them are distorted linear features created when the light from a background galaxy is bent and magnified through gravitational lensing. In the centre left, a particularly prominent example extends vertically about three times the length of a nearby galaxy. A slightly shadowed wedge outlined by a white box leads to an enlarged view at the bottom right. The linear feature is reddish and slightly curved. It is adorned with about half a dozen bright clusters.