Why does my smooth terrain generator not work?

I was eager to find a smooth terrain generator, so i went here and searched smooth terrain. I found this guy's script that had problems with holes, but i took it anyway. I added a few stuff to it, but now it doesn't work. Here's my script:

function smoothTerrain()
    --'loaded' is just a Model filled with all the correctly colored and sized Parts.
    for i, part in ipairs(loaded:GetChildren()) do
        if part.BrickColor == BrickColor.Blue() then
            workspace.Terrain:FillBlock(part.CFrame, part.Size, "Water")
        elseif part.BrickColor == BrickColor.Green() then
            local shape = math.random(1, 2)
            if shape == 1 then
                workspace.Terrain:FillBlock(part.CFrame, part.Size, "Grass")
            else
                workspace.Terrain:FillBall(part.Position, part.Size.Y/2, "Grass")
            end                        -- editing begins here
        elseif part.BrickColor == BrickColor.Yellow() then

            workspace.Terrain:FillBlock(part.CFrame, part.Size, "Sand")
elseif part.BrickColor == BrickColor.Red then
        workspace.Terrain:FillBlock(part.CFrame, part.Size, "CrackedLava")
elseif part.BrickColor == BrickColor.new("Medium Stone Grey") then
    workspace.Terrain:FillBlock(part.CFrame, part.Size, "Slate")
elseif part.BrickColor == BrickColor.new("Dark Stone Grey") then
    workspace.Terrain:FillBlock(part.CFrame, part.Size, "Rock")
        end
    end
end

Does anyone know what i am doing wrong? Thanks so much. Troy