I found a workaround. Not ideal, but it accomplishes what you're after.
copy the word(s) in your original text line you want to animate and paste into its own text box, making sure you maintain the original format when you paste.
Select the text in your new text box and apply the "appear" animation.
Select the text again and change the font color to your desired font.
Click on the highlight box around your new text and use your arrow keys to align it directly over the same text from the original line. (the arrows keys move the text box in such small increments, you will have no issue aligning it over the original)
Now order your animations of your new, changed font text boxes to appear in order.
Do you have proof? – mcalex – 2014-04-22T08:00:07.557
@mcalex I spent several hours fighting against PowerPoint trying to solve this issue, and couldn't find any solution (without using different text boxes for the words I want to change the color) – elunicotomas – 2014-04-28T03:03:24.960