One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,6)(5,8)(9,10)(11,16)(12,23)(13,18)(14,19)(15,20)(17,22)(21,24)(25,26)(27,32)(28,38)(29,34)(30,36)(31,35)(33,39)(37,40) involution — undirected(1,3,4,8)(2,5,6,7)(9,11,15,22)(10,16,20,17)(12,13,21,14)(18,24,19,23)(25,27,31,33)(26,32,35,39)(28,34,40,36)(29,37,30,38)(9,12,13,11,15,21,14,22)(10,17,19,24,20,16,18,23)(25,28,30,39,31,40,29,32)(26,33,34,38,35,27,36,37)(2,6)(5,7)(9,13,15,14)(10,18,20,19)(11,21,22,12)(16,24,17,23)(25,29,31,30)(26,34,35,36)(27,37,33,38)(28,32,40,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.