I had blondish hair when I let my beard grow at the age of about 27. I had tried a couple of times before, but because of the slow growth rate had always given up. It took at least a month before it was at all passable, but has only been shaved off once, for an operatic role. Strangely enough, it started off blonde, but by my late thirties it was quite ginger - it's now only slightly darker than my grey hair.

Unless you have the fast beard growth which is usually associated with dark haired latin descent, just be patient. Give it at least a month and be prepared to do a bit of pruning to keep it even.
Perhaps you'll end up with a magnificent one like Johnny Collins.