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