You must also import the textures and possibly re-assign the materials inside Unity.
Viewing post in Help! (unity importing 3d model)
Materials assigned in blender must be exported in a format that supports them; I think FBX works pretty well, though I haven’t done this type of thing very much.
Otherwise, if you click into Unity’s inspector and go to the mesh renderer on the object that you imported, you should see a few material slots. You can re-create the materials from within Unity itself and assign them here.