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