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