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