It is a bad ideea to make black the logos of the sister projects. The colored logos help the reader recognize them at a glance and also familiarize the reader with them (the color inconsistency could be confusing – somewhere you see the colored version, somewhere else you see the black logo).
Topic on Talk:Structured Data Across Wikimedia/Search Improvements
Hi @NGC 54, thanks for reaching out. Is this happening on a wiki where search improvements have been deployed? I'll send this request to the team, and will let you know as soon as possible. Thanks!
@Sannita (WMF): It happens at ro.wikipedia.org (and probably other wikis), both when logged-in and logged-out; example: https://ro.wikipedia.org/w/index.php?fulltext=1&search=vidr%C4%83&title=Special:C%C4%83utare&ns0=1&ns1=1&ns2=1&ns3=1&ns4=1&ns5=1&ns6=1&ns7=1&ns8=1&ns9=1&ns10=1&ns11=1&ns12=1&ns13=1&ns14=1&ns15=1&ns100=1&ns101=1&ns102=1&ns103=1&ns108=1&ns109=1&ns110=1&ns111=1&ns460=1&ns461=1&ns710=1&ns711=1&ns828=1&ns829=1&ns2300=1&ns2301=1&ns2302=1&ns2303=1.
I see. There has been a request for this with this Phabricator ticket, and it has been done to respect WMF's internal guidelines on logos. You can ask to revert the decision commenting in the Phabricator ticket.
@NGC 54 Maybe you want to see what happens also in this Phabricator ticket, and express your opinion there.