Cancel does not always revert color correctly.

Under any of the following circumstances, the cancel button does not revert the color as it should:

1) typing a color, then `tab`
2) selecting a color in the palette, if `hideAfterPaletteSelect` is `false`
3) or if the api `set` is called.

This is because `colorOnShow` is updated in `updateOriginalInput`, and these 3 circumstances call it. As the name implies, `colorOnShow` should be set only on show, so removing it appears to fix the issue.

I didn't add tests (see #241)