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)(27,30)(28,31)(29,32)(33,35)(34,38)(36,37)(39,40) 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)(26,30)(28,34)(29,35)(31,38)(32,33)(36,39)(37,40)(9,12,13,11,15,21,14,22)(10,17,19,24,20,16,18,23)(25,26)(27,33,35,30)(28,36)(29,32)(31,37)(34,38,40,39)(2,6)(5,7)(9,13,15,14)(10,18,20,19)(11,21,22,12)(16,24,17,23)(25,28,29,37)(26,31,32,36)(27,34,35,40)(30,38,33,39)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.