Ah, I see. The brine for the initial brining of cheese is saturated. But the "brine" which you use to wash wheels of cheese during aging. (Like Linuxboy said, it probably shouldn't be called a brine, since nothing is actually placed IN the solution to brine). Commonly you use a solution of just a few % salt for this, like 1/2 to 1 teaspoon per cup of water, for instance in developing a b. linens rind (whether a slimy smear or a thinner, drier coating). If using a wash to combat mold, then vinegar (w/ or w/out salt) works well, or alcohol, or sometimes a higher salt or saturated brine.
What kind of "colored" spots are you seeing? Really fuzzy? Circular? A natural rind Caerphilly typically develops a mold rind, a mix of whitish to brownish and maybe some blueish thrown in. Bright reds to yellows and blacks though are more trouble though. If it looks like "bad" molds, maybe start with something like 1/2 cup vinegar and 1/2 or 1 teaspoon of salt. Otherwise, caerphilly of similar mold rind are often brushed, not washed.