There are many tutorials by CG Artist about coloring line art. There’s no right or wrong methods about it. It’s about something you want to achieve with your art. This is one of my method in coloring line arts. Enjoy!
First, I scan my line art in RGB format 300 dpi
I use Adobe Photoshop to paint my artwork, after scanning the line art go to Image > Mode > Grayscale and then Image > adjustment > levels, move he slider on the input and output levels to light up the paper and make the lines more visible. After that, I use white hard round brush to erase undesired lines and spots. Cleaning the undesired lines and spots needs a little patience to make the next steps easier. Look at pic.2 for detail.
Double click background layer until it changes into “layer 0”. Then go to Channel tab beside from Layer tab, hold Control (or Command) while clicking Gray Channel Thumbnail. This action will select all of white area.Then press Delete to remove the selected white area. Now you have only outlines on transparent background.
Make a new layer under Layer 0 (outline layer). This layer is for base color. Use paint bucket tool to coloring the area with your desired color. Adjust tolerance value according to outline thickness, check the small box on “All Layers” and uncheck the small box on “Anti Alias”.
You might consider to separate base color layer for the character with base color layer for another object like i did for this picture.
Use CTRL + J (or Command+J) to duplicate the base color layer for the character. On the duplicated layer, adjust color hue and saturation with Image > Adjustment > Hue/Saturation. On lightness bar, lower the lightness while on saturation bar, add the saturation.
Move the adjusted base color layer below the original base color layer for the character .
Decide where the light source in your picture, and use Lasso tool to select where the shadow will cast. On the selected areas press Delete. This action will erase all selected areas and make them the place for shadows. Repeat this action to another area you want.
If you notice the picture, the dark and light area on the picture is still rough, to soften it you can use eraser tool and choose “Airbrush Pen Opacity Flow”. After a little softening-up, now you get better shading for your picture.
Adjust the shadows tone color on the duplicated base color layer for the character using Image > Adjustment > Color Balance until the color feels right.
Repeat step 4 to step 7 on another base color layer.
On outline layer click “Lock Transparent Pixels”. Doing this will enable you to give another color for your outlines.
Use hard brush to colorize the outline.
Find a texture background, you can look for one onCGTexture or from another source.
Put the texture on very top of all layers and change its style to whatever you want. I usually change it to “Multiply”, “Overlay” or “Soft Light” depend on what kind of effect I want. Lower the Opacity of texture layer to make it less contrast.
Select all layers except Background layer, hold Shift while selecting each layer and flatten them using CTRL+E (or Command+E). Use Dodge and Burn tools to make the shading more significant.
Use brush “Airbrush Pen Opacity Flow” to correcting some parts and give color reflection and highlights on each object. The closer an object to each other, the stronger color reflection will cast.
All done. Thank you for reading my tutorial. If you have questions and comment feel free to write it down on the comment below.