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