French called all their "native" African troops "tirailleurs sénégalais" so it is French which create this confusion. They are not just Senegalese but from all French Africa.
In theory and with french troops in ww2 theory maybe far from the true:
When a unit got the word "tirailleurs" in it is mean "native", the tirailleurs could be Sénégalais (ie all black african) Malgache (Madagascar) Marocain, Tunisien, Algerien or Indochinois
Spahi unit are native cavalry unit (can have or not a geographical specification)
Tabor our Goumier are "native" Morrocan mountain infantry
Zouave are by the mid 19th century european troops (but it can be mixed with tirailleurs)
Colonial troops are in theory european troops that serve in the colony so whithes
So are african troops
Most of the officers (but not all) and a large percentage of the NCO are non native so can be some specialised troops within the units
To makes thinks more complexe france in the 20th century do not segregate on the skin color so a french citizen that is black could serve in a standard infantry regiment.
Also it was not uncomon (mainly in ww1) to have a regiment made of battaillon from others unit so we can imagine the case of the regiment of colonial infantry having for a period of time one battailon of colonial infantry and two of tirraileur
In the first French army during the dragoon landing of th 260 000 men there was about 50% native north african 32% european men from north africa, 10% men from black africa and 8% free french from continental france
During winter 44-45 about 137 000 FFI have joined the 1st army
The first army suffered over 9 000 killed in europe (including 40% from north arica)