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