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