Take my picture over there on the left, left click on the mouse, hold it down and drag it around the page. Most captcha pages will allow you to do this.
Drag the captcha code over darker or lighter graphics on the page and you can then read it. The code is transparent, but when highlighted against a dark or light section of the page the code is much easier to read, by about 2x.
Take the "Warrier Forum" black logo at the top of this page, left click and hold, then drag it over the thick red or black line above for another example. We can read that logo just fine, but highlighting a captcha code by doing this same thing helps a lot.
It works, try it next time on those incredibly light captcha codes.