Google Spreadsheets: Conditional formating based on text in another sheet

I'm trying to make a conditional formatting statement based on if a cell is filled with text on another sheet.

For example:

Sheet1 needs to change color of the cell A1 to blue if Sheet2 has text in cell A1

I used a couple of techniques as suggested in other stackoverflow questions, such as: Conditional Formatting from another sheet (I cant find out how to do some sort of regexmatch in this statement)

I thought of some sort of line as (as a custom formula in conditional formatting):

A1(REGEXMATCH(INDIRECT(Sheet2!A1), ""),1 ,0))

but that doesnt work.

Hope someone can help me with this!