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