there are white spaces between elements when adding background color using IOL technique

I don't know exactly what you did because you did not post any code but I can give you an understanding of why these white gaps appear. Using CSS QuickBase uses white borders on the <table> elements used to layout a section. This is a bit unusual and can be difficult to detect as most of the time table cell borders are black or some other visible color.

So you have to set the background-color on the table and the border-color for the cells:

$("table.formSection").css("background-color", "yellow");
$("table.formSection tr td").css("border-color", "yellow");