All surfaces are covered with a material.
Materials are accessed through the material settings dialog where surface behavior is established relative to the rendering engine selected: Internal, OpenGL or LightWorks.
You'll see a "Surface color" box. This color is valid in Internal Engine 3D views and in OpenGL views if textures are not enabled. Any color at all. Doesn't have to be black. We modern.
Otherwise, in Internal Renderings and OpenGL 3D views [with textures enabled] the surface texture provided by an image is used. In LightWorks, depending on how the material is constructed, an image, a shader or a combination of the two is used.
You can extract the color of a Jpeg only by sampling it in Photoshop or similar.
BTW: The Sun color and Ambient color are important to material success - setting these colors also affects the outcome of OpenGL and Internal 3D views.
Dwight Atkinson