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