After a great deal effort I've finally got around to boxing off my new portfolio website:
http://bit.ly/IyiGvB

However I've noticed certain elements are displaying in the wrong colour in Opera. I've read up on the issue a little, and I think Opera might be doing it automatically to create 'more contrast' or something.

Quite annoying! I've attached a screenshot to show how it looks in Opera.

See how the current nav item is grey instead of white, also the logo appears 'lighter' than it should for some reason.

Here is the CSS for #nav:

#nav {
    float: right;
    clear: both;
    font: 3.42857142857143em 'DIN 1451 Mittelschrift Standard', arial, helvetica, sans-serif; /* 48px / 14px */
    width: 100%;
    max-width: 520px;
    background: #222;
    margin-right: -10px;
}

#nav a {
    float: left;
    display: block;
    background: #222;
    padding: .3125em 5% .52083333333333em 0; /* 15px / 48px, 25px / 48px */
    text-align: right;
    color: #fff;
    text-decoration: none;
    width: 15%;
    min-height: 1.5625em; /* 75px / 48px */
}

#nav a small {
    display: block;
    clear: both;
    font-size: 0.29166666666667em; /* 14px / 48px */
    text-transform: uppercase;
}

#nav a:hover, #nav a:active, #nav .current {
    background: white;
    color: #00a2f5;
}

Has anyone else had a similar issue?

That's strange.
Even though the element background is #FFFFFF, opera displays it as grey.
I never run across that kind of problem.

It's pulling #d2d2d2 from somewhere else. I'd be able to tell you, but am absolutely baffled as to the reasoning behind the cleanliness in your code.

Seriously though, who really cares? How many people even use Opera?

Strange indeed! I can set it as red, just not white for some reason.

I can't say it's exactly keeping me awake at night to be honest though