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