I want to bring attention to this old topic, because the problem hasn't gone away (and I guess my eyes aren't getting better with age).
These days I happen to use two different computers interchangeably. One of them is a Macbook with an excellent screen; on this screen I can read the yellow text on grey background without any difficulty. The other one is an Acer laptop with a cheap screen; on this screen the yellow text is barely readable regardless of the font size.
For the record, the colour of background is #848484, and the colour of links is #fcc000. An online tool for contrast checking
says that these colours are not suitable to use with each other.
By the way, in OpenTTD the yellow text always has a black shadow effect. This massively improves the readability, even for small font sizes.