Good point, but when you actually call the interpolation it'll always return the start stop color without fail (because this could only happen when the ``x2 == x1``), which can't happen because this:

```js
rainbowDash({
    1: '#00FF00',
    1: '#0000FF',
    0: '#FF0000'
});
```

Is going to pick either green or blue as the `1` value, not use them both.

I can add a comment to this one (and ``calculateB``) that the `x` values *must not* equal each other.