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)(25,26,30,34)(27,29,33,31)(28,35,38,36)(32,39,40,37)(1,2)(3,6)(4,5)(7,8)(9,11)(10,15)(12,20)(13,22)(14,21)(16,23)(17,19)(18,24)(25,27)(26,31)(28,36)(29,34)(30,33)(32,37)(35,38)(39,40) involution — undirected(2,5)(6,8)(9,12,14,13)(10,16,17,18)(11,20,21,22)(15,23,19,24)(25,28)(26,32)(27,35)(29,37)(30,38)(31,39)(33,36)(34,40)(1,3,4,7)(2,6,5,8)(10,17)(15,19)(16,18)(23,24)(25,26)(27,29)(28,32)(30,34)(31,33)(35,37)(36,39)(38,40)(2,5)(6,8)(9,13,14,12)(10,18,17,16)(11,20,21,22)(15,23,19,24)(25,29,30,31)(26,33,34,27)(28,37,38,39)(32,36,40,35)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.