Conditional formatting, comparing two columns

[blueskyy]

I am at my wit's end.

I have two columns of numbers. Column A and Column B, we'll call them.

I need to look at each number/cell in Column B, compare it to the matching number/cell in Column A. If B>=A, then turn green. If B<A, then turn red.

HOW do I do this? I have tried everything I can think of. x.x

[Zizi64]

First, you need create two cell styles, named (for example) 'Red', and 'Green' based on the default cell style.
Then adjust the properties of the created cellstyles (background color and/or text color)
Finally use the 'Conditional format' option, and set the conditions and the cell styles for the TRUE result...

[Villeroy]

1) Create the 2 cell styles with red and green color.
2) Select the cells you want to format conditionally, say A1:B999. At this point it is very important to notice the address of the active input cell within the selection, say B999.
3) Apply one of the 2 styles, say "Green"
3) Format>Conditional...
<Value is> <Formula Is>: $B999<$A999 and choose the red style.

Like any other formula expression with mixed references, this formula reads: THIS ROW's value in $B < THIS ROW's value in $A and THIS refers to the currently active cell $B999

How to debug a conditional formatting formula:
Select some unused cell range of equal dimensions, say Y1:Z999, and enter your conditional formatting formula with Alt+Enter instead of enter. This will fill the selected cell range with the formula entered into the active cell and you will see which cells get a FALSE or TRUE value.

[blueskyy]

Okay, so by default I made them all green and am focusing on how to get the "less than" cells to turn red.

_A_ _B_
.50 .20
.50 .30
.20 .50
.20 .30

Say this is my table. I need the first two cells in column B to turn red (since .20 and .30 are less than .50) but the other two cells can stay green (since .50 and .30 are greater than .20)

What cells do I select? I tried the formula Villeroy posted but that only affects one cell at a time.

EDIT - So I selected both columns but now both columns have red cells if B<A ... getting closer...

[Villeroy]

You select A1:A4 and the important thing to notice is the active input cell. Of course you need to know what absolute, relative and mixed references are.
[Tutorial] Absolute, relative and mixed references