A style is intended to modify the appearance of the text it is applied to, including colour. You don't want to stop it from doing that. If you don't like the colour it is applying, you should change the style itself. If you want to keep the old style for other documents, but change the colour for a specific document, just make a copy of the style, modify the copy and apply the modified style instead of the original one.
To make a new style, go to the start tab. In the ribbon, there is a section called Styles. In the lower right corner, there is a UI element, a small right angle with an arrow pointing away from it. Click it, and you'll see a floating window listing all styles. Select the style you want to change from the list. Under the list, there are three buttons. If you want to make a copy based on the old one, select the button for creating a new style. If you want to change the old one, select the button for managing styles. A new window opens with yet another list of styles, where your style is still selected. About the middle there is a modify button, click it.
In both cases, you see a new window where you can modify the (new copy of the) style. Under Format, there is a drop-down box where you can select the font colour you like. Choose the colour you like, save your changes and you're done.
If you have a corporate colour scheme and want to use the standard Word 2007 layouts but with your own colour scheme, there is an easy way to do that. In the Styles section of the ribbon under the Start tab, there is the big button called "Change styles". Clicking it opens a small menu. Select colours, and you are given the choice of the typical Word 2007 colour schemata. At the bottom, there is a option called "Create new design colours". There you can set colours for different purposes. Choosing the scheme will change the colours of the standard styles to the new ones, and you can always go back to standard by choosing the "Larissa" integrated colour scheme again.
Disclaimer: As I had to backtranslate from my non-english Word, maybe I've gotten the names of some UI elements wrong, but I guess it will be easy to find them.
edit re: your comment
Styles are meant to change the formatting of text, I don't think there is a way to stop this behaviour. However, I don't see a reason for applying a style at all. Just paste the code and select the option to preserve the original formatting. I just tried with code from Eclipse, I think it will support formatting from other IDEs too.
Also, whatever you are doing, maybe you're trying to solve your problem in the wrong way. I hope you aren't trying to program in Word. If you're writing some sort of coding tutorial, why do you need the code as text? You could include the examples as screenshots. Or you could write the whole thing in LaTeX (if you know LaTeX or if your layout is basic enough), because there are ways to syntax highlight code snippets in LaTeX, or to generate syntax highlighted LaTeX source from a source code. Or if you're that desperate, make the whole thing in HTML. Use CSS for the layout of the generic text surrounding the code, then feed your code through something like Pygments, and paste the HTML output directly into your document; the HTML tags formatting should overwrite the CSS style.
Of course, maybe I'm wrong and there is a way to apply a style in Word without changing the font colour. But I doubt it, it would go against the very purpose of styles.
Press ALT+F9. You're in "Field Codes Mode", where Word displays field codes instead of the values of the fields.
More info: most dynamic data within MS Word is controlled by what Word calls "Fields", and fields are defined by programmatic data called "Field Codes". Field Codes are interpreted commands that Word processes in order to calculate data that is dependent on some value. One reason field codes are used for hyperlinks is that they change color once you've clicked them, from blue to purple, to let you know that you've already visited the site.
Other field codes include page numbers, e.g. { PAGE } and the table of contents, e.g. { TOC ... }.
You probably enabled field codes unwittingly by right-clicking on a field, e.g. a page number, and selecting "Toggle Field Codes" in the pop-up menu.
You can tell that a piece of text is a field (whether field codes are enabled or not) by the gray background that only appears when your insertion point (the blinking cursor) is moved over the field. You can toggle between viewing the field code and viewing the value by pressing Alt+F9 or by right-clicking as I described above.
Best Answer
As far as I know there's no way to redefine it back to the hyperlink colourtheme colour using the Style Modify dialog. However here are two methods you can try.
VBA Method
Alt + F11 to open up VBA Window. Alt + G to open Immediate Window. Then run the following command in the Immediate Window:
ActiveDocument.Styles("Hyperlink").Font.TextColor.ObjectThemeColor = wdThemeColorHyperlink
Style painter method
You can use style painter to copy the formatting back and use that to update the Hyperlink style.
You should now have the hyperlink text back to it's defaults. Check the other Hyperlink text in your document. If you had any other modifications to the Hyperlink style you can now re-apply those.