The redfoot that you have.. that is 'marbling'.. is NORMAL to Brazil. The ones that [ basically the same size ] are NOT 'marbling'.. are NORMAL to "North" of the Amazon river. I speak not in forked tongue.. but in broad generalities! There are "Northern" redfoots and "Brazilian" redfoots and "Bolivian" refoots and who knows where else they have been introduced by man!
Keeping in mind there are always exceptions and extremes - don't expect your "normal" redfoot hatchling to show marbling.. even tho' the parents are Northern X Brazilian cross. You may have hatchlings with the "characteristics" of both.. but I don't think it [ marbling ] is transferable.
I have a few hatchlings "out there" that are "crosses".. I'll ask to see if any are "marbling".
Terry