Amend Joomla Sobi2 Geo Category module

Hi: I have paid for & installed the Sobi2 Geo Category module. I need a small amend so that I can have different coloured markers, based on a custom field I have created, rather than the category it is in. I.e. I have created a custom field which lists 5 different values. I would like the module to show the marker in yellow if 1st value is selected, green if 2nd value is selected, blue if 3rd value is selected, etc. I hope this is clear, but please let me know if you need any clarification.