Each page or spread in your document has its own pasteboard and guides, which are visible in Normal View mode. (To switch to Normal View, choose View > Screen Mode > Normal.) The pasteboard is replaced with a gray background when the document is viewed using one of the Preview modes. You can change the color of this preview background and guides in Guides & Pasteboard preferences.
Document window notes:
Lines of other colors are ruler guides which, when present, appear in the layer color when selected.
Column guides appear in front of margin guides. When a column guide is exactly in front of a margin guide, it hides the margin guide.