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