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