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