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)(11,18)(12,22)(13,20)(14,16)(15,21)(17,23)(19,24)(25,26,31,29)(27,35,37,32)(28,38,36,33)(30,34,40,39)(1,2,4,6)(3,5,8,7)(9,11)(10,15)(12,20)(13,17)(14,21)(16,18)(19,23)(22,24)(25,27,31,37)(26,32,29,35)(28,30,36,40)(33,34,38,39)(1,2)(3,5)(4,6)(7,8)(10,16)(12,23)(15,18)(19,20) involution — undirected(1,3)(2,5)(4,8)(6,7)(9,12)(10,17)(11,20)(13,15)(14,23)(16,22)(18,24)(19,21)(25,28,31,36)(26,33,29,38)(27,30,37,40)(32,34,35,39)(9,11)(10,18)(12,20)(13,22)(14,21)(15,16)(17,24)(19,23)(25,29,31,26)(27,32,37,35)(28,38,36,33)(30,34,40,39)(9,13,14,24)(10,19,16,20)(11,17,21,22)(12,15,23,18)(25,30)(26,34)(27,36)(28,37)(29,39)(31,40)(32,38)(33,35)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.