For several years, in order to change the colour of just ONE word in my site title, I used a simple line of font colour html and it has worked perfectly - see screen grabs:
which rendered the title as:
Since RW8 however, it also adds a bit of text and closing tag at the top left of the page:
And if the code is still the same as posted, try amending the H1 to add in the font attributes as part of the H1 definition; not splitting the line; and omitting the quotes.
Best of all, define a style in CSS (ideally in a separate file, otherwise inline). Good luck!