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