Yeah, how could we get Russia with an african colonial empire?
How about a PoD some time in the 1750s. While France and Britain are fighting the Seven Years War, Spain joins the French side and Russia joins the British. The war lasts a little longer perhaps but as a result, Britain takes Canada as in OTL and Florida, while Russian America is extended as far South as Baja California.
When the Fourteen Colonies revolt, France and Spain move to support the Colonists but Russia attacks Spain, forcing Spain to withdraw and the War of Independence proceeds much as in OTL. In the South and West though, Russia has taken Mexico and now becomes fully enmeshed in the American continent.
Russia has a different concept of slavery to the West and so, when Britain and the US establish colonies for former slaves in West Africa (ie Liberia and Sierra Leone in OTL), Russia does the same, prefering to use peasants from throughout the Russian Empire, rather than import slaves from Africa. Thus, Russia's first African "colony" is established on the West Coast of Africa in the 1830s.
Meanwhile, Russia finds its famous warm water port when it takes Korea in the 1850s, rapidly followed by Japan in 1865. Further expansion in the pacific, taking Hawaii and such Spanish colonies as the Philippines so that,
when the treaty to divide Africa is drawn up in 1906, Russia gets territories in East Africa (that can easily be reached from the Philippines) and perhaps one or two small colonies in West Africa.