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