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