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