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