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