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