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