I use paint.net. How do you make certain colors stand out more than others?

Say if I wanted to do a black and white picture but I wanted to make my eyes bright green. Or if I just wanted to enhance certain colors in a colored picture.I use paint.net. How do you make certain colors stand out more than others?
I don't know anything about paint.net in particular, but most paint programs have the same tools, so I'll answer the question for gimp which you can download for free from www.gimp.org.





You will need to zoom in on the detail you want. Use the gaussian scissors and click around the object you want select. If you go too big, it will get confused, but if you keep the lengths of the individual cuts small, it will correctly follow the line around the object you want to re-color. Once you've closed the loop, you will be able to use the paint tool to fill with whatever color you please.I use paint.net. How do you make certain colors stand out more than others?
If you can use the color wheel or choose any color on some type of palette, choose a color that's further most from black. You have to use more primary colors than mixed colors. For example, if you use pure yellow, red, or blue, it's going to stand out better than secondary colors like orange, green, or purple. If you use other colors than primary or secondary, it would have less impact or less saturation..
When I use Paint.net, I first make a duplicate layer. I use the lasso tool and draw around the eyes. Then I cut the eyes out. I then make the top layer black and white and the green eyes should shine through. You can then just merge the layers together. I downloaded some plugins at the paint.net forum and it has some color enhancer tools that you can just slide back and forth on certain colors. (sorry if this is confusing) I have also found that a lot of the same things you can do with Photoshop you can do with Paint.net. I google photoshop tips and get ideas that way. Hope this helps!