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