smooth out colours

[Ofnuts]

Looking at the Histogram (in "RGB" mode) there are very few color values involved. The range for the blue channel is 5, and the range of the green and red channels is 7-8. Color>Info>Colorcube analysis confirms that there are only 21 colors in the image (outside of the numbers). So, yes, it is normal to have visible transitions, and it is also normal to have visible hue changes because since you are dealing with low values, a change of one unit is important.