The text bellow is somewhat superficial but, it's not my intention (with this guide) to produce an in-depth work on Portuguese colonial uniformology. Roughly what you need to know is that there was no specific colonial uniform until 1899.
It is very difficult to find military iconography of the period so, a lot of digging and gluing of information is needed. Basically, because there was no definite plan for a colonial uniform and many of the units had to resort to the local industries for supplies. What we have to remember is that clothing and equipment tend to degrade very quickly in Africa, and that garrison troops often spent years forgotten in the interior. Metropolitan expeditions tended to wear the same type of uniform as in Europe, with minor alterations, completely unsuited for the tropical climate.
I hope this will be enough to get you started in Portuguese colonial wars. Although it seems a rather limited subject it is, on the contrary, a very complex and fascinating affair. The lack of information available, specially in English, is due to a general unawareness of the wealth of information needing to be rescued from old bookshelves and archives. I will try to remedy this situation with a few articles on various campaigns in Angola, Mozambique and Portuguese Guinea from the mid-1800s until 1920.
In 1899 a new uniform plan was adopted for all colonies. It hoped to standardise the uniforms and equipment of all colonial units and metropolitan expeditions. For campaign purposes the khaki was adopted for all ranks and branches. The headgear was khaki Broad brimmed hats for Europeans and a khaki or red fez for the African contingents. Webbing and equipment was the same as in the metropolitan army except for the African units who had older material. Belts and ammunition pouches were black, bags were grey / khaki, cloth covered metal canteen, small metal pan and a blue-grey greatcoat. The footwear varied among officers, but knee-high boots were the most common. Some officers on campaign also used dark brown leather gaiters. The European infantrymen used boots (with or without gaiters), wile the Africans, who were issued sandals and gaiters, preferred to walk barefoot. During the 1900s campaigns in Portuguese Guinea, many soldiers, because of the tropical humidity, didn't wear the dolman. In its place they used the army issued blue cotton sweatshirt.
The standard rifle of the European units in the 1870s was the Snider. During the 1880s the Snider was replaced by the 11mm cal. Martini-Henry, which was later replaced (at the beginning of the 1890s), by the Austrian made Kropathschek 8mm mod. 1886. The African units used the Snider rifle until the 1890s when they were issued with Martini-Henrys.