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