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