I implore you to take the semantic container approach. :-) When you say "head" I'm not sure if you really mean heading, or in the head area of the document. You almost had it at the start.
But this gives a new paragraph which I don't want.
But you do. :-) You just needs to style out any spacing you don't want.
.some-heads span { color: red; }
p.some-heads { color: blue; margin:0; padding: 0; } <p class="some-heads">blue <span>I am red</span></p>
As I said if this is an actual heading, use the semantic container for it, one of the H family.
<h3 class="some-heads">blue <span>I am red</span></h3>
That will work exactly the same as a <p> - you just might have to fiddle with the sizing a bit.
A note on naming your selectors: try not to use selectors that define an attribute, such as color. If the color changes next week, you will have a confusing selector, span.red might be orange, or blue, or gold . . .
Another reason is sooner or later you will create a selector that conflicts with dom scripting, for example, if you ID a form "search"
<form method="post" action="mysearch" id="search">
it will likely cause errors because search() is a Javascript function - as is submit(). Use names like search-form or submitButton.