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