Changing background cell color to another in calc

Need to change background color in a lot of cells from black to another color (cant do it 1 by 1).
I can do it in excel (with replace tool), but if possible, I would like to do it in Calc.
Is there any easy non-manual way to do it? (I’m talking about thousands cells without any connection to each other)

can’t use mariosv’s solution, because cells contain different content (no string to search for) and a lot of them are even empty, with only background color set

With Ctrl+H (Menu/Edit/Find&Replace)

In Search for: enter the string.

Click Find All, this select all found cells.

You can use Ctrl+1 (Menu/Format/Cells) for call Format Cell box, select the desired background.