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