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