Is there a way to give colour to some words in a full sentense in the header stack in F3?
Yes. Best way would be to create a class (stylesheet) and give it the style you want to apply to the words. Then use something like this in the header stack:
Here goes your <span class="your-created-class">funny</span>header sentence
You can use as many span tags and colours you want. Make every letter in a word different? No problem
I even used that for the word branding in the site title for my navigation bar.