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