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