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