Use the rectangle tool to draw a box that covers the entire page (plus the bleed area). Use the swatches or color panel to choose your fill color.
If there will be other elements on the page, put the rectangle on a bottom layer, and lock it.
Thank you for your answer! I am very new to InDesign, and i thought maybe there were a way to fill the entire page as it is in photoshop,i feel that when you draw a box there are room for error.
InDesign is a page layout program; not a painting program. It works based on objects, and not pixels. You can use the numerical controls after you draw the box to specify its exact placement and size. As long as you include a proper bleed, you will not have to worry about a white edge showing.