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)(11,14)(12,20)(13,16)(15,22)(17,19)(18,24)(21,23)(25,26,32,30)(27,36,38,33)(28,34,29,39)(31,35,37,40)(1,3)(2,6)(4,8)(5,7)(9,10)(11,17)(12,15)(13,16)(14,19)(18,24)(20,22)(21,23)(25,27)(26,33)(28,31)(29,37)(30,36)(32,38)(34,40)(35,39) involution — undirected(1,4)(2,7)(3,8)(5,6)(9,10,13,16)(11,14,19,17)(12,15,22,20)(18,23,21,24)(25,28,32,29)(26,34,30,39)(27,31,38,37)(33,40,36,35)(2,8)(4,6)(9,10)(11,17)(12,15)(13,16)(14,19)(18,24)(20,22)(21,23)(25,29,32,28)(26,34,30,39)(27,37,38,31)(33,40,36,35)(1,4)(2,3)(5,6)(7,8)(9,11,13,19)(10,14,16,17)(12,21,22,18)(15,24,20,23)(25,30,32,26)(27,36,38,33)(28,39,29,34)(31,35,37,40)(1,3)(2,6)(4,8)(5,7)(9,12)(10,15)(11,18)(13,22)(14,23)(16,20)(17,24)(19,21)(25,31,32,37)(26,35,30,40)(27,28,38,29)(33,39,36,34)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.