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