Omage GR306 speakers -- grille removal

Question

The metal grilles on my Omage GR306 speakers are showing rust spots.  I have attempted to remove the grilles to repaint them but the plastic Allen screws that seem to hold them don't seem to be removable.  The screws simply push inward deeper into their sockets when I try to turn or remove them.Can you tell me how to remove the grilles so I can repaint them without having overspray reach the speaker cones?Thank you for your help.RonCan you direct me to anyone that could advise me how best to go about removing the grilles for repainting?