I find the current method very effective in determining both the new posts on the main menu, and on the page of the thread topics.

On the main menu, the icon to the left is blue'ish gray when that forum has no new posts. It turns yellow when someone posts something new. New posts are indicated in the individual thread topics by a down arrow next to the thread. Very Effective. I don't even pay attention to the envelopes.

I don't care for the length of user inactivity required before the "read" posts are renewed, so after viewing the threads I have interest in, I click "mark forums read" at the bottom of the main page. If I stop back 10 mins later, I don't have to remember what I read or didn't read. I just hit reload, or open the browser to RCU, and the icons turn to yellow reflecting new posts since I was last at RCU. This method also makes the refresh rate set by RCU a non issue for me.

I never noticed that the links don't turn another color after being hit, probably because of the method I use to determine new posts. I wouldn't mind if the links changed to a lighter shade of black to reflect visited threads/posts, but only if it was a lighter version of the existing color (which is black). As long as the colors didn't change on the links for posts read, I would be in favor. One thing I really like about RCU is the colors, and hope they don't change for a long, long time.