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