I tried to upload multiple screen shots at once, but instead only added one, so I'm sorry for the random picture. I started up LimeSurvey on my local machine and recreated the issue. I inspected the page, tracked down the HTML element, and went to the CSS file responsible for the style of the link. I changed the color codes for the link and the link when hovered, but didn't change the color of the link after you've clicked it/visited the link. Any value can be put in place of mine, I just found a few quickly that I thought worked pretty well. Here is an album of what I had found, what I changed, and what it looks like. I didn't include an image of what the link looks like when hovered, because I'm running linux on my mac, and have no idea how to screen shot without using the mouse haha. The album has captions, so feel free to read them and get a feel for what I was thinking at the time. http://imgur.com/a/jfOwd. Cheers!

@waltoman : think it's must be fixed only for help tip.

Something like that :
.help a{color:red}

So I've given it another look over and I think I've got it. I just added .questionhelp a{blah blah} and .questionhelp a:focus,.questionhelp a:hover{blah blah}. I left the original a class alone in the CSS and just added .questionhelp a. Here is an imgur album containing the relevant changes. http://imgur.com/a/cTdmP. Let me know what you think!

Works for me. Thanks

https://github.com/LimeSurvey/LimeSurvey/pull/457

LimeSurvey 2.50+ Build 160311 released