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