You can make Keynote change the appearance of a cell or its text when the value in the cell meets certain criteria. For example, you can make cells turn red if they contain a negative number. To change the look of a cell based on its cell value, create a conditional highlighting rule.
Go to the Keynote app on your Mac.
Open a presentation with a table, then select one or more cells.
In the Format 
sidebar, click the Cell tab.
Click Conditional Highlighting, then click Add a Rule.
Click a type of rule (for example, if your cell value will be a date, select Dates), then click a rule.
Scroll to see more options.
Enter values for the rule.
For example, if you selected the rule “date is after”, enter values to specify what date the date in the cell must come after.
Click 
to use a cell reference. A cell reference lets you compare the cell’s value to another cell — so, for example, you can highlight a cell when its value is greater than another cell’s. Click a cell to select it or enter its table address (for example, F1).
Click the pop-up menu, then choose a text style such as bold or italic, or a cell fill such as red or green.
You can select Custom Style to select your own font colour, font weight and cell fill.
Click Done.
Note: If a cell matches multiple rules, its look changes according to the first rule in the list. To reorder rules, drag the rule name up or down the list.
After you add a conditional highlighting rule to a cell, you can apply that rule to other cells too.
Go to the Keynote app on your Mac.
Open a presentation with a table, then select the cell with the rule you want to repeat and the cells you want to add the rule to.
In the Format sidebar, click the Cell tab.
Click Show Highlighting Rules, then click Combine Rules.
Go to the Keynote app on your Mac.
Open a presentation with a table, then select the cells with the rules you want to delete.
In the Format sidebar, click the Cell tab.
Click Show Highlighting Rules, then do one of the following:
Delete all rules for the selected cells: Click 
at the bottom of the sidebar, then click Clear All Rules.
Delete a specific rule: Move the pointer over the rule, then click 
.
Remove a rule from all cells that use it: Click at the bottom of the sidebar, choose Select Cells with Matching Rules, move your pointer over the rule, then click in the top-right corner.