Email Presentation Issues

I am loving the ease of this patform! I have one question/ issue that I can't seem to figure out. 

When I send my emails out after designing and finishing them, all the colors send completely different than how they looked on my browser. This is causing issues like making the background too light or too dark to read, changing font colors, changing button colors, etc..

Why are the colors coming out different when I send the emails, and how can I set colors that will stay consistent when sent?