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