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