Usual culprit is color pink/orange/yellow on page.Following apply to PS6 but earlier PS versions do it just the same.Inkscape has similar options just named differently.
Go to Select->Color Range->Fuzziness
Here with "droplet" selector choose the yellowing pixels (zoom in to find them).They always come in range of yellow shades,this is where trial and error comes in-> adjust with Fuzziness slide bar just how wide is range of offending yellow color. My scans usually need 30-45 fuzziness .
There are 3 droplet selectors.Playing with them can be beneficial but it confuses my train of thought so I often don't use it.
All of above will give you a selection of colors on page to be removed with eraser.Settings you used are still on so do the same step for all pages.
Depending on quality of the scan that usually takes care of issues an desired colors are much brighter.They might seem too bright but printers I use print everything a bit darker than what I see on comp screen so end result is nearly spot on.
It takes some trial and error but that simple method works for me.Image can aways be played with using hue ,saturation and few other adjustments but I never got there.
Have fun
