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