hi lilrainbowsky, welcome to the forum. do your numbers only include -100 to 100? if so, you can select the range you want your conditional formatting (for eg A1:A201), & go to Home -> Conditional Formatting -> Icon Sets -> More Rules ->
Green when value is >= 1
Type: Number

Yellow when value is >=0
Type: Number

Red when < 0

Icon Style: 3 Arrows (Coloured)

if you have a range outside -100 to 100, then you might have to do it outside the cell, say in Column B.
=IF(AND(A1>=1,A1<=100),CHAR(227),IF(A1=0,CHAR(226),CHAR(228)))
you can then do a conditional formatting on this range by going to Home -> Conditional Formatting -> New Rule -> Use a formula to determine which cells to format -> Format values where this formula is true:

=B1=char(228)
font will be red for this

=B1=char(226)
yellow font

=B1=char(227)
green font