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