gistfile1.js

columns: [
    'item',
    'cost',
    {
        key: 'price',
        allowHTML: true,
        formatter: function (o) {
            var words = o.value.split(/\s+/),
                i = words.length,
                word;

            while (i--) {
                word = words[i].toLowerCase();

                if (word === 'mark') {
                    // wrap the word with an element with a css class.  Put the
                    // colors or other visual treatment in the css for that class.
                    // Note words[i] is used on the RHS instead of word to preserve case
                    words[i] = '<span class="mark">' + words[i] + '</span>';
                } else if (... other conditions ...) { ... }
            }

            return words.join(' ');
        }
    }
]