Colour alternate rows without disturbing existing format

I would like alternate rows to have different background colour. I used conditional formatting to achieve the desired result by having a new style that had background colour defined for the cells. However, the problem is that the existing format of the cells get disturbed. e.g. if I have cells with zero decimal places, they get redefined with the number definition of the new style used for background colour fill.

Is there a way by which existing style gets used except that only the background colour is filled for alternate rows?

Google spreadsheet provides a more user friendly conditional formatting process and wish the same is replicated here.

You can use a macro, to only set the background colour property.

see: colorCalcCellsSelection as an example.