But you could always have 3 vertices for each of those triangles, so 9 verts instead of 5. This is useful if you want all three triangles to be a single, different colour for example, rather than the mesh having a smooth colour gradient along each triangle from vertex to vertex.
You colour each vertex, not each triangle - and then the triangle is coloured by all 3 vertices it's made up of. So if a vertex is used in more than one triangle, all the triangles it's used in will be coloured by it.
You colour each vertex, not each triangle - and then the triangle is coloured by all 3 vertices it's made up of. So if a vertex is used in more than one triangle, all the triangles it's used in will be coloured by it.