Harley wrote:
As for styling, I'd like a full beard eventually but don't think I want to try any other styles. 

My questions are, do you think this will fill in and darken as I get older, or is there anything I can do now? Also, do you think that growing it out longer will help to hide it a bit more or just look thin and scraggly on the cheeks, drawing attention to it? 

Here's what I think:  If the pics you show are your beard after 9 months perhaps a full beard is not in the cards for now.

I do have to comment on your trimming it up though.  That will not help as far as fullness or bulk.  Yes, growing it out longer will make it look less thin.

I do not know if you are totally averse to consider anything other than a full beard, but you have plenty of coverage if you wanted to consider a circle beard or a Van Dyke beard.  On the other hand if you are set on growing a full beard you should do it.  I would advise though that if you want to go the full beard route that you not trim it at all during the development stage.  It may look a bit untidy but that will pass if you let your beard grow. As far as colors in your beard it is totally normal to have multiples of colors in your beard.