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