In this jam each color that has it's own "color code" is considered a separate color. However, there is an exception to this in the rules. Rule: "Gradients are allowed but no more than 3 objects/sprites/backgrounds in total with a gradient and the two main colors from the gradient count towards the 10 color max.". So basically you can still do shading with gradients but you have to follow that rule. Btw you could also do shading using dithering.
Both wouldn't be allowed because when I say gradient I mean something like this . It Goes from one color to a different color and the two main colors (green and brown) count towards the 10 color max and if it's part of the sprite the two main gradient colors count towards the 2 color max for the sprite.
Probably a silly question, and I'm not even sure if I'd even try to take advantage of this but can a single sprite swap the two colors in use for another set of colors, still in the 10 color pallette limit?