Try this code:

The reason is that $pad() counts the $rgb() characters. Most of the time it can be fixed by placing the $rgb() before the $pad, rather than inside it, but in a few cases I wasn't able to.

Such as this:
$pad($repeat($rgb(255,0,0)♥,$get(rating)),5,·)

That code wouldn't work as expected anyway, as the "·" would be red also.

I would use either:

$progress2($get(rating),5,5,$rgb(255,0,0)♥,$rgb()·)

... or, more code but less processing (unnecessary repeating of colour codes), and the code I would personally use:

$rgb(255,0,0)$repeat(♥,$get(rating))$rgb()$repeat(·,$sub(5,$get(rating)))

I do agree that $rgb(255,0,0) should not be treated as a string though .