The first three pictures are of the Blue Wildebeest and the last two are the Black Wildebeest.
No, they are not actually blue and black. I sometimes wonder at how these things ever got their names. :)
Of the two the Blue Wildebeest is more widespread as it survives very nicely in most bush areas. The Black Wildebeest is mainly found along our west coast as it prefers, drier, semi-desert conditions.
Horns grow sideways out of its head
Has a black tail
Has no crest of hair on its nose
Darker in color
Horns grow forward
Has a white tail
Has crest of hair on its nose