C#: Interpolate between 2 colors - 2 different approaches taken from StackOverflow.com

interpolate_colors.cs

// Interpolate between 2 colors in C#
// Taken from answer by user Jason
// http://stackoverflow.com/questions/1236683/color-interpolation-between-3-colors-in-net
class ColorInterpolator {
    delegate byte ComponentSelector(Color color);
    static ComponentSelector _redSelector = color => color.R;
    static ComponentSelector _greenSelector = color => color.G;
    static ComponentSelector _blueSelector = color => color.B;

    public static Color InterpolateBetween(
        Color endPoint1,
        Color endPoint2,
        double lambda) {
        if (lambda < 0 || lambda > 1) {
            throw new ArgumentOutOfRangeException("lambda");
        }
        Color color = Color.FromArgb(
            InterpolateComponent(endPoint1, endPoint2, lambda, _redSelector),
            InterpolateComponent(endPoint1, endPoint2, lambda, _greenSelector),
            InterpolateComponent(endPoint1, endPoint2, lambda, _blueSelector)
        );

        return color;
    }

    static byte InterpolateComponent(
        Color endPoint1,
        Color endPoint2,
        double lambda,
        ComponentSelector selector) {
        return (byte)(selector(endPoint1)
            + (selector(endPoint2) - selector(endPoint1)) * lambda);
    }
}
// -----------------------------------------------------------------------------
// More generic function:
// Taken from Answer by Steven Jeuris
// http://stackoverflow.com/questions/13252838/get-colors-between-two-color-hex-refs-or-rgb/13253304#13253304
// What you are looking for is called interpolation. In this particular scenario you need to interpolate data between two key points.

// Since interpolation is a really common scenario when programming, I wrote a generic solution for it, easily allowing you to interpolate between two or more key points, using either linear or even cardinal spline interpolation.

// Using my library you could calculate intermediate colors as follows:

var keyPoints = new CumulativeKeyPointCollection<Color, double>(
    new ColorInterpolationProvider() );

keyPoints.Add( Color.FromArgb(0, 250, 154) );
keyPoints.Add( Color.FromArgb(143, 188, 139) );

var linear = new LinearInterpolation<Color, double>( keyPoints ); 

// // E.g. to get a color halfway the two other colors.
// Color colorHalfway = linear.Interpolate( 0.5 );
// You would have to implement ColorInterpolationProvider by extending from AbstractInterpolationProvider<Color, double>, but this is quite straightforward, and more information can be found in my blog post.

// This example uses the Media.Color class, but you could just as well support any other Color class by passing along a different interpolation provider.

which library do you refer to?