I haven't found any tip like this on this forum nor in the help file and so I thought I might share what I found out.
When you are tracing a picture finding the right color might turn out difficult (esp. for beginners). When your want to use the exact colors you can load the picture you are tracing right into the color picker with
Custom Picker --> Load Custom Picker --> file-you-are.tracing.jpg
Works fine for me!