Most of Spains African colonies are not good candidates.
The Spanish did'nt control Western Sahara in full until the mid 1930's while Rio Muni (the mainland portion of Eq. Guinea) did'nt become a full colony until the beginning of the 20th century (having been a Protectorate from 1885-1900) and was in general not a place Europeans would want to settle due to the presense of a large enough native population, the climate and malaria not being conductive to large scale settlement and the fact it was a de facto slave port into the 1920's.
Now, Spanish North Africa (IE the Rif region) would be a good area for settlement, heck Queen Isabella actually passed a proclomation forbidding it because poor Spaniard farmers were moving there.
Annobón and Bioko (frm. Fernando Po) are also both good candidates, though the former mose so than the latter.
Guinea-Bissau is pretty much a no-go, it was only fully conquered in 1915, by which point it had a good sized native population (est. 440,000) that was still more than a little restive and at the time Portugal did'nt really have alot of people willing to settle (Metropolitan Portugual only having a little under 6 million people) and those that were willing to move primarily went to Brazil and the United States while those willing to settle the colonies went to the islands and Angola mostly.
Cape Verde, which is majority Mestiço (mixed race), and São Tomé and Príncipe, which is ethnically and racially diverse and used to have a sizable white population, are both good candidates to become situations where larger immigration leads to Whites, while a minority, having a majority of power, though this would be different from elsewhere as the white population would be more like 30-40%.
Angola and Mozambique are both good candidates as well.
Mozambique had a long established white population, which at independence was numbered at 350,000 (3.3% of the population) and a large Mestiço minority as well.
Angola originally had a relatively small population (6.6 million in 1975) and was starting to draw in a good deal of European immigration in the mid-20th century onwards, with 360,000 Whites (5.4% of the population) at independence and even today Whites and Mestiços each make-up 2% of the population a pieace.