Selective Colouring

[gloriousxleader]

Hello,

I'm doing my first ever project in GIMP, and it's a map for an original setting I'm making. I've reached a barrier, however. My map is as follows:
YdwJeE4.png

[For access to the multilayered GIMP file, see the following download link:
https://drive.google.com/open?id=1xt...aPvddYXy3IdkdM ]

I want to be able to paint portions of the map. So for example, I want to turn the top of the left continent white to reflect an arctic biome. However, I can't find a way to ONLY paint the green part. I could zoom in and carefully paint it white with a brush, but I feel like there's a tool to select portions of an image and recolour them. Do you have any guidance?

[Azélor]

Welcome to the Guild.

Normally, I would use multiple layers such as the land and water would have their own separate layer.
I assume you must have several layers because the different effects you used you usually be done not just on a single layer.
If that is not the case and you used only one layer, then it's trickier.

What your looking for is probably the magic wand tool.

[gloriousxleader]

I figured it out.

My method:
1. Select the layer with only the continental landmasses on it.
2. Select by color > Click anywhere on one of the green landmasses.
3. Selection > Quickmask
4. Selection by Color > Click the green landmasses.
5. Paintbucket > Black > Green landmasses [this doesn't paint them black, it just deselects them]
6. Paintbrush > Color: White > Fill in the area I wanted to select.
7. Exit quickmask
8. Paintbucket the biome color into the selected area.

The end result:
LQu9dCo.png