Practice makes perfect. The more often you can manage to do the above exercise, the more skilful you will become.
When you have learnt to remember the colour of your choice try to send it - project it - into certain parts of your body.How? You can imagine the colour/energy leaving your hands and flowing from your fingertips, or you could send it from your third eye, the space between your eyebrows, or from your heart chakra. Or you could find your own technique. You could also send it to somebody else. This activity is called: ABSENT HEALING.
When you become more skilful in doing colour healing for yourself and/or others you will develop intuition. This is a feeling, an inner voice, which guides you toward the most appropriate colour and where to send it.