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