Change the color of single word of selected text with keyboard shortcuts?

Not really, no. 

Text color is controlled by CSS. You would need to wrap your text in a set of <span> tags that also have a class added to them. That class would then have a selector in your .css file with the color property and whatever value you'd like to set.

You could create a wrapping Snippet of a set of span tags with a class, then highlight the text you want to change to a given color and double click the Snippet in the Snippets window to add it to the text...

1. Open your Snippets Window under Window > Snippets (or hit Shift + F9)
2. Click the New Snippet button (document with + icon) in the bottom of the Snippets window
3. In the dialogue that appears, give the Snippet a name, like Red Text
4. Ensure "Wrap Selection" is active
5. For "Insert Before" add something like... <span class="redtext">
6. For "Insert After" add in... <span>
7. Click OK
8. Between the page's <style> tags or in your .css file, add the selector...
  .redtext{color:red;}

From there on out, while working on that page or site, you can highlight text in Design View and doubleclick the Red Text snippet to wrap the selection in the span tags and turn it red.