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