I've been searching through some listings and found a few PCGS slabbed coins with the comments of questionable colour UNC details.
What does this mean when they refer to that. Are they implying the coin was wizzed, cleaned, dipped? What would companies like ICCS or CCCS describe it as (I haven't seen this designation on their slabs before)
It means that the color of the coin might indicate intentional enhancement.
Such a designation limits the potential buyers pool significantly as many collectors simply don't want anything that's details or similar.
New collectors still finding their feet might consider them bargains. Even if the price is low most of those collectors who become more knowledgeable will wish they hadn't spent their money on "bargains".
For bronze coins, this is probably fatal. For UNC details silver coins, it theoretically may be possible to crack them out of the slab, dip them to remove toning and resubmit them to a different TPG for grade. Remember, as NGC claims, dipping isn't cleaning. (I disagree with NGC on this.)