I want to make a suggestion for coloring
In the animation, some color lines are used to distinguish shadows and highlights.
Hello and welcome to the forum 
I don’t think this would be an ‘animation’ tool thing, it seems more like a colouring tool or technique thing.
What technique do you usually use to colour your lineart?
Can you produce and post simple coloured lineart images that illustrate and explain the effect and end result you want to have?
I have a feeling that this should be in a separate topic.
My immediate (and simple) thought would be to use the Fill Tool with Grow Selection adusted to go over the lineart.
For what I understood, in animation you use different colors to define shadows/light limits
Says light red and light blue:
But in krita, onion skin doesn’t allows to make distinction between different lines:
I think what is asked here is to apply a kind of filter that will allow, in onion skin, to make distinction between black lines, red lines and blue lines.
Grum999
Hello, thank you very much for your reply, I am an animator, I will use krita to make original animations at work
In animation production, lines of different colors are used to distinguish shadows and highlights and to distinguish color blocks, which will speed up the coloring speed
Thank you for the detailed explanation.
I think this would be a large development effort, if it was done, and it would need lots of discussion with developers and other animators.
You’ll need to wait for other comments and further discussion.
At the moment, can you pass artwork/animations between krita and paintman or opentoonz to perform some functions on one and other functions in another?
When you say “it” what are you referring too? You mean the onion skin to absorb those colors?
Fill tools 
On the topic of binaziration of colors i did make a weird suggestion to perhaps aid with that before.
I am gonna take a look at paint man to see what you do there.
Well it helps saying what your referring to explicitly… because coloring can mean various tools to place color or even filters or perhaps the filling color of the rendering of something else like the onion skin.
Coloring does not equate to fill tools.
Thank you for your help
Currently I am painting keys production in krita, export to paintman for animation and coloring
I was taking a look at what paintman was because I never heard of it before. This is what it is in case someone is curious too.
https://m.youtube.com/watch?v=OPHGpk4KlAk
This should give a picture of what is needed in terms of output from krita into it. But honestly it feels more like a source of inspiration for krita features also.
The Fill tool is a simple but effective colouring tool.
At the moment, the only way I can think of to use it would be for the shading colour guideines to be on a separate layer and use Grow Selection to cover them, but not cover the black.
You’d do the final visible artwork in black:
Then copy that layer and put it underneath and add the shading colour guide lineart:
Then you’d add a layer for Fill colouring, under the final lineart and set the Grow Selection value to cover the colour guide lineart. For this, the black lineart should be a greater width that the colour guide lineart:
As you can see, you’d need to adapt your colour guide lineart to the characteristics and limitations of that method.
It would be difficult/impossible to retrofit that technique to an existing animation and would be something you’d need to do from the very start.
There’s nothing wrong with passing work between different applications, as long as you don’t lose information and as long as it’s not too complicated and confusing.
Grow selection distorts the edges of the lines though.
Wobbly lines is something you can’t afford in animation.
Yes it does. But you can anticipate that and construct your multi-layer lineart to avoid/cover that, subject to line thickness limitations.
The technique I showed is far from ideal but it’s the only ‘workaround’ I can think of in the absence of the ‘ideal’ requested feature.
Let’s hope we get that one day.
I am not sure if there is a work around currently.
I eventually do want to make small animations in krita and this is a topic that has been putting me off from 2d.
Thank you very much for your help
Grow selection will make the edges unable to maintain binarization
So it’s hard to use in business processes
This is just my suggestion 
Thanks again
Sorry, I made some mistakes，This will not happen with binarized lines
I just saw this guys.
topic related but what has been done on the blender side related to painting traditional animation.
I do think this is really good thing to have for animation.
Not sure how it could be done in Krita though, but considering Krita is meant for traditional artists and now traditional style of animation it does seem within scope to be contemplated at least.
