One vertex per element, one color per generator, with an edge from x to x·s.
(6,7)(10,11)(14,17)(15,19)(22,24)(23,27) involution — undirected(2,4)(5,6,9,7)(8,11,12,10)(13,14)(15,20)(16,17)(18,19)(1,2)(3,4)(6,7)(10,11)(13,14,16,17)(15,18,19,20)(21,22,25,24)(23,26,27,28)(5,7,9,6)(8,11,12,10)(13,14)(15,18)(16,17)(19,20)(21,23)(22,26)(24,28)(25,27)(5,8,9,12)(6,10,7,11)(13,15)(14,18)(16,19)(17,20)(21,24,25,22)(23,28,27,26)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.