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