title: glColorPointer() not painting vertex color in interleaved VBO
body: <p>I am using (Python and PyOpenGL) interleaved VBO (vertex, normal, color) in the form:</p>
  
  <pre><code>Vx1, Vy1, Vz1, Nx1, Ny1, Nz1, R1, G1, B1, A1, Vx2...
  </code></pre>
  
  <p>VBO is generated with:</p>
  
  <pre><code>self.vbo_id = glGenBuffers (1)
  glBindBuffer(GL_ARRAY_BUFFER, self.vbo_id)
  
  #    upload data to VBO
  data = model_loader.Model_loader(filename = "geometry.STL")  
  self.N_vertices = len(vertices)
  
  alpha = 1
  color = np.array([[0.1, 0.1, 0.1, alpha]], dtype='float32')
  colors = np.repeat(color, self.N_vertices, axis=0)
  
  VBO_data = VBO_reshape.create_VBO_array(data.vertices, data.normals, colors, GL_primitive_type = "triangle", interleaved_type = "true")
  VBO_size_bytes = arrays.ArrayDatatype.arrayByteCount(VBO_data)
  
  glBufferData(GL_ARRAY_BUFFER, VBO_size_bytes, VBO_data, GL_STATIC_DRAW)
  glBindBuffer(GL_ARRAY_BUFFER, self.vbo_id)
  </code></pre>
  
  <p>Geometry from VBO is drawn with the code:</p>
  
  <pre><code>v_pointer = ctypes.c_void_p(0)
  n_pointer = ctypes.c_void_p(12)  
  c_pointer = ctypes.c_void_p(24)
  
  v_stride = 40
  n_stride = 40
  c_stride = 40
  
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, self.vbo_id)
  # enable vertex array
  glEnableClientState(GL_VERTEX_ARRAY)
  glVertexPointer(3, GL_FLOAT, v_stride, v_pointer)
  
  # enable normal array 
  glEnableClientState(GL_NORMAL_ARRAY)
  glNormalPointer(GL_FLOAT, n_stride, n_pointer)
  
  # enable color array 
  glEnableClientState(GL_COLOR_ARRAY)
  glColorPointer(4, GL_FLOAT, c_stride, c_pointer)
  
  glDrawArrays(GL_TRIANGLES, 0, self.N_vertices)
  
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0) # reset
  
  glDisableClientState(GL_COLOR_ARRAY)
  glDisableClientState(GL_NORMAL_ARRAY)
  glDisableClientState(GL_VERTEX_ARRAY)
  </code></pre>
  
  <p>The geometry (vertices and normals) are drawn correctly (see figure below). I want to paint each vertex with different color but is not painting any colors? Any suggestions how to draw color of vertex with <code>GL_TRIANGLES</code> and calls to <code>gl_DrawArrays()</code> and <code>glColorPointer</code>? Do I have to use shaders or can this be done without shaders? If I understand correctly it can be done without using shaders.
  <img src="https://i.stack.imgur.com/RHLez.png" alt="enter image description here"></p>