Select the cells that you want to format
Choose Format>Conditional Formatting
From the first dropdown, choose Formula Is
In the formula box, enter a formula that refers to the active cell:
=B2/INT(B2)=1
Click the Format button
Select the formatting you want for integers, click OK
Click Add
From the first dropdown, choose Formula Is
In the formula box, enter a formula that refers to the active cell:
=B2/INT(B2)<>1
Click the Format button
Select the formatting you want for integers, click OK, click OK
Note: numbers with .0 will be highlighted as integers