I always think colours are a personal choice, but colours that are faithful to what was available at the time will never hurt values. For me, I've always taken the colour as first delivered.
My Fulvia Colour Sample cards (no date but between 66-69) give the following:
Bianco Saratoga (an off-white)
Grigio Vinovo
Grigio tor di Valle
Turchese Mereveld (a green)
Blue Mendoza
Blue Lancia
Giada Bettole (a sort of cream)
Verde Ostenda (very dark green - almost black)
Nero
Amaranto Montebello (a dark wine red)
Argento Nevada
Blue Jamaica
Rosa Mirabello
However............I also have several UK sales brochures from the late '60's and not all colours are listed as being available in the UK, so if you really want to keep the pedants of your back you may have to check what was available in SA
I have the codes for most of the above if you need them
Note that the sort of cream colour quoted above should be Verde Giarda Bettole. Cheers Tom