You have to take into account that cold air is denser. Therefor, your altimeter will indicate less then the actual altitude. This can be checked while on e very cold day performing your outermarker check on an ILS, you will read a lower altitude while being perfect on glide. If I remember well, it is a correction of 1%/4°C.
For the speedindicator, I don't know by heart. But, if I think logically, the speed is total p - static p. Because both pressures will be affected by the cold, I don't think there is a correction to be made. (I could be wrong on this one !!!)
Concerning your Mach indicator. The lower your temperature, the lower speed equals mach 1. Thus, for a constant true airspeed, flying into colder air will increase your machnumber.
For hot air, it's all the opposite of course.
I hope my simple explanations are any help to you, it's been a long time since I had to do this stuff.. <img src="wink.gif" border="0">