Please open attached test page with QtTestBrowser.exe on Window. If I specify input field color as <input value="bug" style="color:#EEEEEE;" />, I will see nothing. I can see correct text while specify input field color as <input value="bug" style="color:#646464;" />. The issue happens to both QtWebkit 2.3 and Qt5 on Windows. Mac doesn't have the issue.
Created attachment 197740 [details] test page
Unless I misunderstood the problem, it seems to me that it'll be the same problem on all ports and browsers, there's not much we can do about poor web design choices.
Qt 4.8/QtWebkit 2.2 doesn't have the issue.