One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,8)(4,6)(5,7)(9,10)(11,16)(12,18)(13,26)(14,31)(15,20)(17,22)(19,29)(21,32)(23,34)(24,35)(25,39)(27,37)(28,33)(30,36)(38,40) involution — undirected(1,3,5,4)(2,6,7,8)(9,11)(10,16)(12,24)(13,27)(14,21)(15,23)(17,36)(18,35)(19,38)(20,34)(22,30)(25,28)(26,37)(29,40)(31,32)(33,39)(1,4,5,3)(2,6,7,8)(9,11)(10,17)(12,21)(13,28)(14,24)(15,23)(16,26)(18,33)(19,35)(20,37)(22,29)(25,27)(30,40)(31,38)(32,39)(34,36)(2,7)(6,8)(9,12,15,14)(10,18,20,31)(11,21,23,24)(13,25,30,29)(16,32,34,35)(17,33,37,38)(19,26,39,36)(22,28,27,40)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.