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