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