There are 2 colour charts that you can use as visual reminders:
1) Customer Colour Chart - When you open a customer record under the customer tab, there is a grey dot under every customer's name. Click this dot for a colour chart and select a colour to remind you of anything you need to remember about that customer. You create your own colour key but, when you next select that customer, the coloured dot will appear next to their name.
2) Booking Colour Chart - In the top right corner of the Cost section of the booking, there is a little blue dot. Click this dot and a colour chart will be displayed. When you select a dot from the chart, it will be added to the booking in the calendar to remind you of anything you need to remember about that booking. The colour of the dot can be updated in the calendar mode by hovering over the dot and selecting a new one.