Monochrome

I've seen so very often black and white photographs and only a specific part is in color, green, red, yellow etc. What is this effect called and how you do that? I have PSCs6 and NIK software. Thanks

I use Lightroom to do this.
LR has an area where you can adjust saturation for each color separately. I would just then de-saturate all colors except the one I'm interested in.

This link could give you an idea.
http://www.photoshopes​sentials.com …and-white/hue-saturation/

You need to select the area you want to keep coloured and convert the rest to black and white (to your taste - you have a lot of choice in BW conversion, not just desaturation) and then adjust the coloured part to your taste. It's the selection of the area that is (usually) manual and the rest are just colour adjustments - i.e. there's no specific name for the process...

The 'effect' or technique is usually referred to as 'selective coloring'.