# 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 4)
    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()

# 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()

# get project instance
p = QgsProject.instance()

# get layout manager
m = p.layoutManager()

# get layout from manager
layout = m.layouts()[0]

# get layout items
items = layout.items()

# iterate through layout items and find map
for item in items:
    if isinstance(item, QgsLayoutItemMap):
        break
        
mapItem = item

# change the background colour by passing an RGB QColor object
mapItem.setBackgroundColor(QColor(60,255,240))

# refresh the layout to apply change
layout.refresh()

# 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 4)
    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()