I doubt Mexico would have any interest in Africa, when there's still the north-west to colonise, and the Pacific. As someone suggested, it would take a particularly eccentric Mexican dictator with a strong economy behind him and a major colonial chip on his shoulder to try claiming African colonies.
Here are a couple of randoms:
- Brazil somehow claims Angola and/or Mozambique from the Portuguese. There were settlements of returned Brazilian slaves all along Africa's west coast in OTL, so such a proposition isn't entirely out of the question.
- When the USA relieves Spain of Cuba, she takes the outposts on Equatorial Guinea with her. Come Cuban independence, these are handed over to the Cuban Government. Pretty wild, TBH: it's more likely that the Americans would either keep said outpost to herself, or sell it to someone else. Possibly Liberia?
- A more stable, less-gimped Haiti embraces an ideology of back-to-Africa, claiming strategic points on the African coast for trade purposes. These colonies would be tiny (given the limits of the Haitian economy), but if they're clever they can pick up a couple of choice outposts worth holding onto.