Once you've got a few people on, the month view is a lot of jobs that all look the same. You can give anyone on your team a colour, and their work gets shaded with it on the diary.
It's off for everybody to start with. Nothing changes until you turn it on for someone.
Give someone a colour
Settings → Team → People. Tap the person, and under Diary colour pick one of the ten. It saves as you tap — there's no Save button.
To take it off again, tap the crossed-out swatch at the front of the row. They go back to looking like everyone else.
You need the manage team permission to change it.
Where you'll see it
On the Diary on a computer — the week grid, the day timeline and the month view. Their jobs are shaded with a light wash of their colour.
You'll also see it back on Settings → Team → People: the circle with their initials in it goes their colour, so the list tells you who is who before you go and look at the diary.
The phone diary is left plain on purpose. It shows one day as a list with everyone's initials down the side, so it's already telling you whose is whose in words.
Worth knowing
You don't have to do everyone. Most owners only ever mix up two or three people. Colour those two and leave the rest — a diary where everybody's painted is no easier to read than one where nobody is.
A pencilled job still looks pencilled. The shading goes underneath the hatching, so a provisional booking in someone's colour still reads as provisional.
On the week grid the colour follows the row. If you've put someone on a job as a helper, the card in their row carries their colour, because that's their afternoon. On the month view there are no rows, so a job takes the colour of whoever is leading it.
Their initials go the same colour on the team page. So the team list doubles as the key for what you're about to read on the diary. Anyone you haven't given a colour keeps the usual dark chip.