Had the same problem. Orange / Black Rib but could only find White hatches.
HOWEVER, these people (International Marine Supplies - 01427-891144) are very helpful and do white hatches which they paint black, they sell the hatches and paint and actually make hatches for a rib manufacturer which are white painted black!
They will even spray them for you and say the paint will not flake off - they are used in harsh environments!
Very helpful on the phone.
Note: Some white hatches cannot be painted, must be the correct hatch material and type of paint (outboard paint I think)
Hope this helps