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