If you are happy to adapt your mark-up you could wrap your whole string of text within a span.
HTML:
<h3 class="title">
<img src="/imgs/small-logo.png" width="31" height="30" />
<span>Test</span>
</h3>
<h3 class="title">
<span>Test</span>
</h3>
CSS:
h3.title {
color: #004265;
}
h3.title span {
display: inline-block;
}
h3.title span:first-letter {
color: red;
}
:first-letter
only works on block level elements, hence setting the span to inline-block
.
Here is the working code - JsFiddle