BUY IT HERE:
http://www.amazon.com/gp/product/B001BQZSZ4?ie=UTF8&t...
FreshAirsoftReviews presents a review on the Leapers 40mm red/green dot scope purchased off airsoftgi.com for around $35. The scope has 5 different brightness settings on both the red and green colors. The scope is primarily made of metal and adds a nice amount of weight to the gun.

One things you may have to worry about when buying this scope is that it is pretty low and you may need a rail raiser like I did to get it working.

All in All this scope is a good starter red/green dot scope because of the price and has many high quality settings.

You can get it at:
http://www.airsoftgi.com/product_info.php?cPath=36_117&am... (less info)