The nominate race in South Africa is locally referred to as the Blue-billed Firefinch. The cock has a deeper red, and his belly and undertail is charcoal

whereas the hens is buff (cock left)

 
The crown, head and neck is dark grey, more pronounced in the cock bird (cock left)            

In eastern Africa we find the subspecies haematocephala, locally referred to as the African Firefinch. There pattern is similar to rubricata but with more intense red and charcoal areas replaced by jet black which is probably why they are sometimes referred to as the Kulikoro (cock left)                      

In this subspecies the hen still shows the grey crown, whereas on the cock bird the red extends over the crown (cock left)


So just to compare the two subspecies, in rubricata the cock has a grey crown, and in haematocephala it has a red crown (cocks left)  

Other than the difference in the crown, vent and overall intensity of the red the birds are very similar  

Comparison of the cocks (rubricata left)              

Comparison of the hens (rubricata left)