For a print or photograph, the hand coloring is typically done in a watercolor-like paint or ink. For vases and porceline, the hand color may be done in a different kind of paint.
If the colors are hand painted, the ink consistancy and darkness will be uneven, like with a watercolor painting. As the brush applies the paint, the paint is distributed unevenly, with darker areas here, lighter there.
In most but not all cases, if the colors are printed, a color almost always will be solid.
A halftone reproduction of a hand colored item will reproduce the tonal pattern of handcoloring, but is easily identified as a reproduction. If you take a microcope or strong maginfying glass, there will be a multi color dot pattern in the image.
Of note, if two extra colors are added an item is ‘tinted.’ If three or more extra colors are added it’s ‘colored.’