hot and cold water reversed

In my new house (built 1981), the hot and cold water are reversed in the main floor powder room sink and the kids' bathroom tub/shower. All other sinks and showers are normal. Both 'backwards' faucets show hot on the left and cold on the right as normal, but have to be operated reversed.
It appears that the pipes to the reversed sink and shower are installed normally. That is, the pipe on the left (as you face the faucet as if you're using it) goes directly into the left/hot knob and the right pipe directly into the right knob.
I was able to fix the sink by installing new steel-braided flexy pipe (not sure what it's called) from the copper pipes to the faucet and crossing them. But I can't do this for the tub faucet, where the copper pipe runs directly into the faucet connections.
I would be very surprised then that the pipes were installed reversed, which makes me wonder if the faucets themselves somehow mix the hot and cold backwards. Are there faucets that do this intentionally, or is there some way to configure a faucet to mix the water backwards?
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Michael Press wrote:

If they are Moen (pull knob out to turn on and increase flow, and turn right/left for Cold/Hot) then the knob can simply be taken off and the cartridge stem rotated 180 degrees.
Jim
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Michael Press wrote:

probably somewhere down the line the pipes had to be fixed for some reason(maybe a freeze or somthing) and the guy who fixed it put the wrong pipe to the wrong pipe... and later(if it was the occupants), said oh, well i will get to the fix later at least we have water and never did get around to fixing it))..
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message

reversed in

tub/shower.
faucets show

to be

One in my new house was like that. A single knob controlling both hot and cold. I told the builder. He took the knob apart, reversed a part, put it back together. Worked fine.
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