G&G M4's are what you want
Zero One & a G&G Raider - tough decision the long or short barrel version ?
2-tone is free of charge - most places charge for 2-toning
or if you are one of those people that MUST have a metal M4
(even though the polymer abs G&G Combat Machines are the dogz nutz)
http://www.airsoftworld.net/g-g-gc16-30th-anniversary-limited-edition-aeg-airsoft-rifle-black.html
now you have to pay a bit for the two-tone but they do a nice snake-skin 2-tone on this full metal mofo
Those are my 2 top choices for buying a 2-tone starter M4
if you get ukara'd as we say - then you can go nutz on an all black or tan Realistic Imitation Firearm....
But be warned buying these rif toys can get very addictive but there is 2 great 2-tone starters for you