As explained (somewhat) by the phrase 'day meets night in your eyes', 'radium eyes' probably means that whoever he's singing about has eyes that, at different points in time, are both dark and light. (Pure radium, when fresh, is a brilliant white, but it blackens when it's exposed to air.)
As explained (somewhat) by the phrase 'day meets night in your eyes', 'radium eyes' probably means that whoever he's singing about has eyes that, at different points in time, are both dark and light. (Pure radium, when fresh, is a brilliant white, but it blackens when it's exposed to air.)