INDEX - inaccurate color association

[barrubba]

i'm indexing an illustration with a 72 color palette.
The palette has a lot of colors covering well the color spectrum of the input illustration.
So I would expect to see all colors well associated after indexing.
Instead some of them turn very much despite the palette was equipped with colors very close to them.
An important example is light blue in attached files
How to solve?

[rich2005]

The problem is there there is no similar colour in the colormap. Using your 72 colour palette for indexing, the colormap is a good match.
However...
The available indexed colors do not have anything close to the blue in original RGB image so it uses the nearest. You can select from the colormap and you can paint or fill that selection but only using the colours in the colormap. 

   

edit: I painted in a bit using that lighter blue (and a bit in yellow) as an example.