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