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