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