code: public static void glBlendColor(float r, float g, float b, float a)
      {
          checkContextCompatibility();
          nglBlendColor(r, g, b, a);
      }
docs: The {@link #GL_BLEND_COLOR} may be used to calculate the source and destination blending factors. The color
  components are clamped to the range {@code [0,1]} before being stored. See {@link #glBlendFunc(int, int)} for a
  complete description of the blending operations. Initially the {@link #GL_BLEND_COLOR} is set to {@code (0, 0, 0,
  0)}.
  
  @param r Specifies the red component of {@link #GL_BLEND_COLOR}.
  @param g Specifies the green component of {@link #GL_BLEND_COLOR}.
  @param b Specifies the blue component of {@link #GL_BLEND_COLOR}.
  @param a Specifies the alpha component of {@link #GL_BLEND_COLOR}.