Implementing a parser, with the following code, will produce the desired effects but will be expensive.

Expensive? How much text are you putting out to the screen before the "inefficiency" is noticeable? It's a little premature to be optimizing at this time.

Not to mention I feel like I'm reinventing the wheel.

But consider what you were doing with the code you posted. You want to attron a color pair each time you encounter a yellow escape sequence. That seems like quite a customized requirement.

You're using Curses and Term::ANSIColor, so you're leveraging a lot already = good for you! I did a cursory search and couldn't find any more helpful modules beyond those two.

I'd write formatted_text() using a dispatch hash. Also made the regex quantifier non-greedy:

my %esc2action = (
    color('yellow') => sub { attron(COLOR_PAIR(1)) },
    color('reset') => sub { attroff(COLOR_PAIR(1)) },
);

sub formatted_text {
    my ($win, $text) = @_;

    # tokenize text on escape sequences
    for my $token (split /(\e\[[^m]+?m)/, $text) {
        my $act = $esc2action{$token};

        if ($act) {
            $act->();
        }
        else {
            addstr($win, $token);
        }
    }
}
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