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