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)(11,23)(12,27)(13,20)(14,21)(15,18)(16,22)(17,26)(19,24)(25,39)(28,36)(29,35)(30,37)(31,34)(32,38)(33,40) involution — undirected(1,3,5,4)(2,6,8,7)(9,11,14,26)(10,17,21,23)(12,16,24,15)(13,29,30,28)(18,19,22,27)(20,36,37,35)(25,32,40,31)(33,38,39,34)(1,3,5,4)(2,7,8,6)(10,18)(11,24)(12,26)(15,16)(19,27)(20,34)(21,22)(25,29)(28,40)(31,32)(35,36)(37,38)(1,3,5,4)(2,7,8,6)(9,12)(10,19)(11,16)(13,25)(14,24)(15,26)(17,22)(18,23)(20,33)(21,27)(28,31)(29,32)(30,40)(34,35)(36,38)(37,39)(1,4,5,3)(2,6,8,7)(9,13,14,30)(10,20,21,37)(11,25,26,40)(12,28,24,29)(15,31,16,32)(17,33,23,39)(18,34,22,38)(19,35,27,36)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.