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