Yes, the problem seems to be in the color. Not sure why, though:

//string onmouseoverStyle = "this.style.backgroundColor='00BFFF'"; // Deepskyblue
string onmouseoverStyle = "this.style.backgroundColor='blue'";

Commented code doesn't work and this code works, but I want my color to be lighter.

Do you see what's wrong?

Thanks a lot again, I think I would switch to a method later.

UPDATE. My colleague found the problem in a second.

It should be:

string onmouseoverStyle = "this.style.backgroundColor='#0bf'"; // Deepskyblue

missed # in front.