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