Two questions regarding layer masks and replacing colors

[Armonster]

1. How do I make a detailed layer mask so I can place a part of one image onto another image. There is only two colors (shades of green and the color black) so it should be easier than most of the tutorials I am finding online. How can I do this since I only have two colors?

2. Also, how can I replace any color/shade of a color with a different color? Besides using the color replacement tool, is there a way to replace all instances of green and shades of green with the color white?

 

[$1r_M4x1mu$]

Hi Armonster

Welcome to PSG

1. the easiest way will be isolating the color to be removed via selection"color range", or got to the channels palette and select the channel whit more defined contrast in between the colors usually red channel "RGB" Mode. and use that channel as layer mask

2. Same technique used before works in both cases.

*EDIT
Forgot to mention in the second case, if the image to be changed involve only 2 colors the color to be changed and "black or white" just use HUE/SATURATION and use sliders to change color values.