Chlorocebus is a genus of medium-sized primates of which seven species are currently recognized.
The seven species look very similar and were therefore formerly classified as a single species.
These seven species are:

1. Green Monkey (Chlorocebus sabaeus), found in West Africa;
2. Tantalus Monkey (Chlorocebus tantalus), found in Ghana to Sudan and south into Uganda;
3. Vervet Monkey (Chlorocebus pygerythrus), found in southern and East Africa.
4. Bale Mountains Vervet (Chlorocebus djamdjamensis), found only in Ethiopia;
5. Grivet (Chlorocebus aethiops), found in Ethiopia, Sudan, Djibouti and Eritrea;
6. Dryas Monkey (Chlorocebus dryas), found only in the Congo Basin; and
7. Malbrouck (Chlorocebus cynosuros), found in DR Congo, Angola and Zambia.

In Uganda both Tantalus Monkeys and Vervet Monkeys occur. 
However, in Uganda the Vervet Monkey is only found in the southeastern part of the country (Lake Mburo area).
An important difference between these two species is the black end of the tail in Vervet Monkeys versus the white/gray end of the tail in Tantalus Monkey. 
In most of Uganda you will find the subspecies budgetti of the Tantalus Monkey which have pretty dark hand and feet.

Enjojo Lodge, Ishasha area, Queen Elizabeth National Park, Uganda, 21 January 2025