I remember seeing a Chumash that showed the shoresh highlighted for every word, does anyone know what this Chumash is called (and where it can be purchased)?
I have a (paper) book called אמרי מדריך that seems to be what you're looking for. It highlights the shoresh, showing the other letters in outline, and it includes letters from the shoresh which were dropped in conjugation in minuscule type. The book is entirely in Hebrew and I can't read the introduction, so I don't know what other notational conventions they are using. (I can't read the footnotes either, alas.)
I do not remember where I got it, but it now appears to be available online (h/t DoubleAA). This sefer is also printed in full in the back of the Artscroll Chinuch (children's) Chumashim. Those Chumashim are available in every Jewish book store.
Here is a sample inside:
Here is the full cover page:
And the back side, which shows a copyright date of 2005 and a name and address: