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