How to increase number of colors in colorbar, and how to draw boundaries of regions?

I have this scatterplot, obtained through this command.

scatter(longitude,latitude,15,VR1,'filled');colorbar;

The blue regions are not very visible. How can I make the regions more distinguishable? One way to do that is by increasing the number of colors to include red, purple, etc and their finer shades. Is this possible?

Another way would be to find and mark the boundary of the different regions. How can I do that?

Answer 1

[Adam]

doc colormap

allows you to change the colourmap that is used. You can either choose from already created Matlab colourmaps or define your own n*3 array of colours.

doc caxis

allows you to change the colour compression (essentially how the data maps onto the given colourmap)