def colors_to_string(colors):
    """Transform the 3 sized tuples 'colors' into a hex string.
    
    [(0,100,255)] --> 0064ff
    [(1,2,3),(4,5,6)] --> 010203040506
    """
    return ''.join(['%02x%02x%02x' % (r,g,b) for r,g,b in colors])