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