Creating spread-out colors

Question

I'm drawing graphs with Microsoft Chart Controls and I'm trying to generate different colors for each line in the graph (up to about 15-20 colors). If there are 14 lines to be drawn, I want to create a different color for each one of them.

Now, I've tried this with using HSV:

private Color GetSeriesColor(int seriesIndex,
                             int seriesCount)
{
    return ColorHelper.FromHsv(360.0*seriesIndex/seriesCount, 1, 1);
}

The problem is however that the green and blue colors look very similar:

Is there a way in C# to create x colors that look different to a human?

Answer 1

You could try dual pointers, each pointing to a different place in the spectrum. At least this way you'd end up with alternating colors.

private Color GetSeriesColor( int seriesIndex, 
                              int seriesCount, 
                              int steps ) {
    return ColorHelper.FromHsv( 
        ( 360.0 / steps ) * ( 1.0 * seriesIndex / seriesCount ) + 
        ( ( seriesIndex % steps ) * ( 360.0 / steps ) ),
        1, 1 );
}

Calling code:

GetSeriesColor( 5, 18, 2 );

This will create two "pointers". The first will start at position 0, the second at position 180. The function will alternate between the two pointers, giving a sort of "checkerboard" look to the graph.

If you don't like the effect, your best bet might be a color palette (stored in an array) with x number of predefined colors, looping when you've reached the end (or possible adding shading, such as darker colors to lighter colors).

EDIT
I'll add, though, that using color coding willy-nilly is often a poor design choice. You'd be better off using labels directly on the graph, if possible. Beyond about 8 colors the human eye begins to have trouble differentiating between them. See https://ux.stackexchange.com/questions/17964/how-many-visually-distinct-colors-can-accurately-be-associated-with-a-separate.