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