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