colorStuff.fs

    type RgbColor = {r:int;g:int;b:int} with
        static member create r g b = {r=r;g=g;b=b}
        static member fmap f left right = {r=f left.r right.r;g=f left.g left.b; b = f left.b right.b } 
        static member (-) (l,r) = RgbColor.fmap (-) l r
        static member (*) (l,r) = RgbColor.fmap (*) l r
        member left.squaredDistance right = 
            let diffColor = (left - right)
            let squaredColor =  diffColor * diffColor
            diffColor.r + diffColor.g + diffColor.b
            
    type NamedColor = {name:string;color:RgbColor} with
        static member create name r g b = {name=name;color = RgbColor.create r g b}

    let similarColors (knownColors:NamedColor seq) (maxCount:int) (colorFrom:RgbColor):NamedColor seq = 
        knownColors 
            |> Seq.sortBy (fun x -> x.color.squaredDistance colorFrom)
            |> Seq.take maxCount

    // this should probably come from a database
    let knownColors = 
        [
            NamedColor.create "Black"     0   0   0
            NamedColor.create "Blue"      0   0 255
            NamedColor.create "Green"     0 255   0
            NamedColor.create "Cyan"      0 255 255
            NamedColor.create "Red"     255   0   0
            NamedColor.create "Magenta" 255   0 255
            NamedColor.create "Yellow"  255 255   0
            NamedColor.create "White"   255 255 255
        ] 
            
    RgbColor.create 12 50 255 |> similarColors knownColors 3