Have you ever wanted currency in Excel to be red when it's negative, so your bad budgeting mistakes leap out at you quickly? Well that's easy: just select the cell, hit Ctrl-1, and choose "Currency" on the Number tab. Pick one of the red options. No biggie.
The downside to the currency format though is it is a bit crowded - the currency symbol is mashed right against the number, and the number's mashed right against the margin. So some people prefer to select Accounting instead. It gives you great indenting and plus it replaces "0" with "-", which looks super-slick.
But it has a downside too! In accounting there is no red ink (which strikes me as ridiculous, btw). So how do you get the great arrangement of Accounting with the cheerful judgement of the colour red? Easy: just paste this in the Custom box:
_-$* #,##0.00_-;[Red]-$* #,##0.00_-;_-$* "-"??_-;_-@_-
This concludes today's tiny Excel tip which managed to become an entire blog post.