15 William (formerly known as the William Beaver House) at 15 Williams Street at the Northwest corner of Beaver Street in the financial district of Manhattan, was given a nickname by the AIA Guide to New York City (Fifth Edition) (2010):
   
“The Post-it Note building: 47 stories of apartments clad in distinctive alternating swatches of black and bright yellow glazed brick.”
 
15 William has frequently been included in discussions about New York City’s ugliest buildings.
 
   
Wikipedia: 15 William
15 William, formerly known as the William Beaver House, is a 47-floor condominium apartment building located at 15 William Street at the intersection of William Street and Beaver Street in the Financial District of Manhattan, New York City. It opened in 2008, at which time it was the only ground-up residential development in the Financial District. It was designed by the New York firms Tsao & McKown and SLCE Architects, with interiors and public spaces designed by SPAN Architecture and Allied Works Architecture and developed by SDS Investments, André Balazs Properties, and CIM Group. The building is 528 feet (161 m) high, and includes 320 units.
   
Architecture and design
The building has a brick exterior with dark grey and gold panels between the windows. Shears and staggers in the building, together with subtle disruptions in the building’s facade, were incorporated to diffuse light down the streets of lower Manhattan and position apartments to get the most light and views in a part of the city that is densely built. Its general appearance has earned it the nickname “The Post-It Note Building”.
           
Google Books
AIA Guide to New York City (Fifth Edition)
By Norval White & Elliot Willensky with Fran Leadon
New York, NY: Oxford University Press
2010
Pg. 16:
William Beaver House, 15 William Street, NW corner Beaver St. 2009. Tsao & McKown architects.
The Post-it Note building: 47 stories of apartments clad in distinctive alternating swatches of black and bright yellow glazed brick. Daring amidst the financial district’s monochromatic canyons, the idea here was to (Pg. 17—ed.) create an entire interior world,  luxurious buffer against the hustle and bustle of the City’s street life.
 
Curbed—New York
Top 10 Bitchiest Architecture Reviews in the New AIA Guide
By Joey Arak Jun 2, 2010, 4:12pm EDT
Somebody finally has something nice to say about controversial architect Robert Scarano, and surprisingly, it’s the gatekeepers of one of the most respected texts on NYC architecture! This week the fifth edition of the AIA Guide to New York City gets dropped on the brains of archigeeks everywhere (careful, it’s 1,055 pages), and this latest version of the beloved manual is full of surprises?such as the praise not only for Scarano projects like ScarBow and Long Island City’s Vere (which the authors already let us know they were digging), but also the hilarious ways in which the book takes swipes at those buildings deemed unworthy.
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5) William Beaver House (Tsao & McKown Architects): “The Post-It Note Building.” [photo]
 
Curbed—New York
What’s the Ugliest Building in New York City?
Sound off
By Amy Plitt@plitter Jun 17, 2016, 10:45am EDT
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Here are some possible contenders, which, in the interest of fairness, we lifted from the 2010 edition of the AIA Guide to New York City. Truly, it is extraordinary in both its breadth and its bitchiness:
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William Beaver House: This Financial District condo gets the moniker “the Post-It note building.” That’s … not wrong.
 
GlobeSt.com
CREW New York Takes An Architectural Tour: Slideshow
By Betsy Kim | August 30, 2018 at 04:00 PM
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For additional anecdotes, behind, (adjacent to) or within New York City buildings and structures, view the photo gallery. If you want to remember the CREW New York tour, the images include the Financial District condominium nicknamed “The Post-It Note Building.”