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