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