I found this link - it is of any help
http://www.deskdemon.com/pages/uk/services/colourcodetipsI also think that it comes with experience and also different companies use different calendar systems so you have to get used to them pretty quickly, with no training. I too have learnt on the job - and always found that most systems are similar and also fairly intuitive.
She maybe can find some online tutorials if she knows what system the company uses (can ask during the interview what system they use). Or once she has a job, can use the Help function and take time out during lunchtime or after work to read through the basics.