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