Setting background color in print layout from Python console in QGIS

Question

I would like to change the background color in my print layout from the Python console in QGIS. I can see some of the background color (currently white) near the corners of my layout and I would like to change this color.

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I tried adding the suggested code to my for loop but was still getting the white background. Here is my code (see the # Change background color section at the end):

for i in range(1):# Testing
    
    # Load Raster File
    fn = "/".join([fldr, targ[i]])
    fi = QFileInfo(fn)
    fname = fi.baseName()
    rlayer = iface.addRasterLayer(fn, fname)
    
    renderer = QgsSingleBandPseudoColorRenderer(rlayer.dataProvider(), 1, shader)
    rlayer.setRenderer(renderer)
    
    # Create and Export Print Layout
    # Identify Layer for Map
    layers = QgsProject.instance().mapLayersByName(fname)
    layer = layers[0]
    project = QgsProject.instance()
    manager = project.layoutManager()
    layoutName = " ".join(['Temp Pred Maps', str(i)])
    layouts_list = manager.printLayouts()
    
    # Remove any duplicate layouts
    for i in layouts_list:
        if i.name() == layoutName:
            manager.removeLayout(i)
    
    # Add add layout to QGIS
    layout = QgsPrintLayout(project)
    layout.initializeDefaults()
    layout.setName(layoutName)
    manager.addLayout(layout)
    
    # Change background color
    layout = manager.layouts()[0]
    items = layout.items()
    for item in items:
        if isinstance(item, QgsLayoutItemMap):
            break
        
    mapItem = item
    mapItem.setBackgroundColor(QColor(60,255,240))
    layout.refresh()

Answer 1

If you want to have the same map background color as the page, you can disable background color for the map item.

mapItem.setBackgroundEnabled(False)

Answer 2

# these only need to be assigned once, so I moved them out of the loop
project = QgsProject.instance()
manager = project.layoutManager()

# get current extent of map canvas (you may want to use a different extent, this was just for the example)
ext = iface.mapCanvas().extent()

for i in range(1):# Testing

    # Load Raster File
    fn = "/".join([fldr, targ[i]])
    fi = QFileInfo(fn)
    fname = fi.baseName()
    rlayer = iface.addRasterLayer(fn, fname)
    
    renderer = QgsSingleBandPseudoColorRenderer(rlayer.dataProvider(), 1, shader)
    rlayer.setRenderer(renderer)
    
    # Create and Export Print Layout
    layoutName = " ".join(['Temp Pred Maps', str(i)])
    layouts_list = manager.printLayouts()
    
    # Remove any duplicate layouts
    for j in layouts_list:           # changed i for j to prevent confusion with the i in outer loop
        if j.name() == layoutName:
            manager.removeLayout(j)
    
    # Add add layout to QGIS
    layout = QgsPrintLayout(project)
    layout.initializeDefaults()
    layout.setName(layoutName)
    manager.addLayout(layout)
    
    # create map item
    mymap = QgsLayoutItemMap(layout)
    mymap.setRect(20, 20, 20, 20)
    mymap.setCrs(rlayer.crs())
    
    # add layers to map
    ms = QgsMapSettings()
    ms.setLayers([rlayer]) # set layers to be mapped 

    # set the map extent from the map canvas (line 6)
    mymap.setExtent(ext)
    
    # arbitrary map scale, will need adjusting
    mymap.setScale(250000) 
    
    # change background colour (RGBAlpha)
    mymap.setBackgroundColor(QColor(60,255,240,255))
    
    # add map to layout
    layout.addLayoutItem(mymap)

    # adjust the size of map
    mymap.attemptResize(QgsLayoutSize(200, 200, QgsUnitTypes.LayoutMillimeters))
    
    # refresh the layout
    layout.refresh()