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