Theo also had to take care of the last part of the animation.
Composing and Editing!
This was an essential part of the production.
It is commonplace for the frames to be completed on a computer.
After they are drawn and checked, they are digitized. Once they are on the computer, they are painted with a specified color palette by the painting staff.
They use the shading lines drawn by the key animators to do the shading colors.
This digital equivalent of the 'ink & paint' stage of production, which used to be done by hand, has allowed some more interesting visual styles to come through in the coloring, such as the use of gradient shading or even textures.
These would have been too difficult to do back in the day.
It has also saved considerable time and money in the process.
These become the final "cels" that go into the animation.