I am in the process of building my first AR. Well i started off buying a PSA PA10 stripped lower. The next thing im going to order is the Lower parts kit. but i have no idea what to look for and if all or any other brands would interchange with PSA.. and also the only color i can find is black but im wanting brown... anyone know anywhere i can look? please help. im in no hurry to buy the parts thats why im building my own i have to save up money and i also want to build it like i want instead of how someone else wants it..