A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

cold as stone • stone cold
cold as stone —(also: cold as a stone) 
1
. very cold to the touch:
Laura reached for Paul’s hand but when she laced her fingers
in his, Paul’s hand was cold as stone. 2. (of a person) not much
moved by emotions: He was all sweet and kind to me but I
remained cold as a stone! “You take pleasure in tormenting
me,” he said…
Note: 
The expression does not correlate in meaning with the
phrase cold as a wagon tire—(U.S. dated sl.) dead: The first
time she saw a man lying cold as a wagon tire wasn’t the day
she first stepped into battle, which was a good thing.
stone cold —
1
. said of cold tea, coffee, etc. that is expected
to be warm: He used to talk so much that his food was usually
stone cold before he finished it. 2. = cold as stone 
1
: The only
observation I was left to ponder was how I could sweat so pro-
fusely while my hands were stone cold.
cold cash • hot money
cold cash —(also: cold hard cash) money in its proper form,
as distinguished from checks, etc.: A Chinese buyer walked
into his atelier and paid cold cash for a monumental statue
(which can go for up to a million dollars).
Note: 
The expression does not correlate in meaning with the
phrase cool million—(coll.) a million dollars considered as an
asset or a lump sum: You can bet he isn’t short on cash now.
Each cast member earned a cool million bucks every time an-
other episode of the hit TV show was shot.
hot money —money that is moved by its owner quickly from
one form of investment to another: Hot money is flowing into
Kenya as the country emerges as the latest target for interna-
tional fund managers looking for high returns.