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