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