Observed colour of stars in the field likely to be of early type (as estimated from their 2MASS colours) against their Gaia EDR3 distances (Bailer-Jones et al. 2021). The thick (red) line is a 200-point running average. There is an obvious decrease in the number of objects around d ≈ 2.8 kpc, which coincides with a steep increase in the average colour. The shaded area represents the running standard deviation. See the text for the many biases present.