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