merge_colors

/// merge_colors(col1,col2,...,amount)
//
//  Returns a color merged from a series of two or more colors
//  controlled by the given amount. A value of 0 returns the
//  first color, a value of 1 returns the last color, and values
//  in between return a blend of two adjacent colors in the series.
//
//      col1        first color
//      col2        next color
//      amount      blend factor, 0 to 1
//
/// GMLscripts.com/license
{
    var colors = argument_count-1;
    var amount = clamp(argument[colors], 0, 1);
    var n = amount * (colors-1);
    var col1 = floor(n);
    var col2 = col1 + 1;
    return merge_color(argument[col1], argument[col2], frac(n));
}