There is no proceeding before OHIM to challenge a mistakenly accepted seniority claim. Alternatively, you can challenge the trade mark directly in its respective country.  

For more information please read National Law Relating to the Community Trade Mark and the Community Design, Chapter 7 National provisions on the effect of a seniority claim.

It appears to follow from this that, where a national mark contains a disclaimer or a colour claim but the corresponding Community trade mark does not, the respective marks do not then satisfy the 'triple identity' rule. In such circumstances the resultant seniority claim cannot be challenged.