How to pass mesh colors (with Learn OpenGL model.h)?

in the case of the learn opengl model.h how would you then pass the per mesh colours?

Do you mean this?:

At first glance, a Vertex doesn’t currently contain a color:

struct Vertex {
    // position
    glm::vec3 Position;
    // normal
    glm::vec3 Normal;
    // texCoords
    glm::vec2 TexCoords;
    // tangent
    glm::vec3 Tangent;
    // bitangent
    glm::vec3 Bitangent;

So you’d probably need to add that (if you needed the color value to vary per vertex).

If you didn’t need it to vary per-vertex however, you could use a constant vertex attribute value.