Gimp color with pencil shading

Question

How do I add color to a pencil drawing and leave the pen/pencil shading alone? ( color white under pen/ pencil shading and leave shading untouched on top)

Answer 1

Here's another simple method.

1. Add a white filled layer under your pencil drawing layer.

2. Set the blend mode of the pencil sketch layer to "Multiply"

3. Add a transparent layer between those two layers.

4. Paint the colour on the transparent layer.

Answer 2

1. Sample the color of your background (use an average)
2. Add an alpha channel to your layer if not there already Layer>Transparency>Add alpha channel
3. Set the Bucket-fill too to Color erase mode (Mode selector at the top of the Tool options) and bucket-fill the image with your sampled background color. This will make the background transparent (checkerboard pattern)
4. Set the Bucket-fill tool to Normal mode again, create a new layer and fill it with your sampled background color
5. Drag that layer below the drawing layer in the Layers list

When you have done this, you should see your initial image, but now the pencil is on its own layer. To change the pencil color:

• Set the "alpha-lock" on the drawing layer (checkerboard icon at the top of the Layers list)
• Paint the layer (brush, bucket, airbrush...): the alpha-lock will maintain the opacity of pixels and transparent pixels won't be altered