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