"S/+, pb/pb" literally means "blue ghost" ;) The full version should be "+/+,S/+,+/+,+/+,+/+,+/+,+/+,+/+,pb/pb"
S means blushing (stipeless, aka ghost) from father and + means wild-type (in this case stripes) from mother. pb/pb means "blue" from both parents, which is recessive, so quite a lot...