This brought back memories! I spent long hours playing Colt 36 on my MSX computer when I was a kid 
Here's a video of this awesome game: https://www.youtube.com/watch?v=ipql3AasR6E
Fun fact: my parents bought the MSX computer with a monochrome green phosphorus monitor, so I never knew that the machine could do color until I found the computer on a closet many years later and connected it to a color TV. I spent that day trying out all the games from my childhood and marveling at their colorfulness!