I actually think the colours are pretty good. Tan and blue are a good contrast so I'd tick with that as a base and then add faded greens and brown to the land with the airbrush tool to map in different terrains.
Someone's going to say it so I'll jump in first. Rivers. They don't fork as they flow downstream. Also, if there is a lake, there's a river from it that connects to the sea. These are definitely things you need to fix.
I like the symbol set - very clean and neat. I'm a little confused by the dotted lines - are they roads or boundaries?
Finally, welcome to the guild! Post a welcome note in the appropriate forum but it's good to have you here already. Nice first map, and a little bit of rep to get you going.
PS you can attach files to the forum directly using the attachment manager - the paperclip at the top of the post editor when you compose a post. Definitely better to do that than link to an external site.