hum ideas pl;ease

i have had people write on this cast so i can keep it as a memory of what i have been through but on the purple one that im going to be geting i told my lil niece she coudl decorate it any way she wasnt any ideas of what woudl show on purple besides what crayon are apreciated i know they have new colored sharpie markers but im not sure any are bright enough for the purple cast but she really wants purple  she has actually been the main cast colr choser for this surgery her and mom picked the yellow and she said she liked the putple as well and it just happens to be one of my favoraite colors