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