There is no clear origin for the term:

Big Blue is a nickname for IBM. There are several theories explaining the origin of the name. One theory, substantiated by people who worked for IBM at the time, is that IBM field representatives coined the term in the 1960s, referring to the color of the mainframes IBM installed in the 1960s and early 1970s. “All blue” was a term used to describe a loyal IBM customer, and business writers later picked up the term. Another theory suggests that Big Blue simply refers to the Company’s logo. A third theory suggests that Big Blue refers to a former company dress code that required many IBM employees to wear only white shirts and many wore blue suits. In any event, IBM keyboards, typewriters, and some other manufactured devices have played on the “Big Blue” concept, using the color for enter keys and carriage returns. (Source: IBM article, Wikipedia)

The name of the computer, “Deep Blue,” is a reference to IBM’s nickname, “Big Blue.”

It uses the color orange in not only its logo, but also its buildings and even the aprons that its employees wear, turning the color into the signature color for the company.  The company is occasionally referred to as “Big Orange,” which is a reference to calling IBM “Big Blue.”

Today, the chain is for all practical purposes non-existent with only a handful of locations still remaining.

It uses the color orange in not only its logo, but also its buildings and even the aprons that its employees wear, turning the color into the signature color for the company.  The company is occasionally referred to as “Big Orange,” which is a reference to calling IBM “Big Blue.”

“DOT” can be an acronym for the departments of transportation.  Depending on context the acronym ”DOT” usually is preceded by other letters indicating the particular government that it is part of.  For example, “USDOT” for the federal-level Department of Transportation, “IDOT” for the Illinois Department of Transportation, “PennDOT” for the Pennsylvania Department of Transportation, and “WSDOT” for the Washington State Department of Transportation.

It includes agencies such as the Federal Aviation Administration (FAA), the Federal Highway Administration (FHWA), the Federal Railroad Administration (FRA), and the National Highway Traffic Safety Administration (NHTSA). Former divisions that are now part of the Department of Homeland Security (DHS) are the United States Coast Guard (USCG) and the Transportation Safety Administration (TSA).

The USDOT also sometimes uses the acronym “DOT” as state departments of transportation do in some contexts where the particular agency involved is clear.

And I turned, and lifted up mine eyes, and looked, and, behold, there came four chariots out from between two mountains; and the mountains were mountains of brass. In the first chariot were red horses; and in the second chariot black horses; And in the third chariot white horses; and in the fourth chariot grisled and bay horses. Then I answered and said unto the angel that talked with me, What arethese, my lord? And the angel answered and said unto me, These are the four spirits of the heavens, which go forth from standing before the LORD of all the earth. The black horses which are therein go forth into the north country; and the white go forth after them; and the grisled go forth toward the south country. And the bay went forth, and sought to go that they might walk to and fro through the earth: and he said, Get you hence, walk to and fro through the earth. So they walked to and fro through the earth. Then cried he upon me, and spake unto me, saying, Behold, these that go toward the north country have quieted my spirit in the north country.—The Bible, Zechariah 6:1-8 (King James Version).