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