Applying standard, random, categorized colours

Question

I have applied random categorized colours to several lines (streets), based on the street ID, so that each street shows in adifferent colour.

I now want the same colours to be applied to the house numbers (point). I have the street ID in the layer of the house numbers, but i can't fint a way to apply the same colours to the house numbers that was used for the streets. I.e. if a street has randomly been appied red, i want all the houses (point) on that street to also have the colour red.

Answer 1

Starting from a categorized layer, through this custom function:

from qgis.core import *
from qgis.gui import *
from qgis.utils import iface

@qgsfunction(args='auto', group='Custom')
def get_catg_color(value, feature, parent):
    """  
    <h2>Example usage:</h2>
    <ul>
      <li>get_color("nomeCampoCategoria") -> '228,52,199,255'</li>
      <li>get_color(to_string(format_number("nomeCampoCategoria",2))) -> '228,52,199,255'</li>
    </ul>
    """
    
    layer = iface.activeLayer()
    renderer = layer.renderer()

    if layer.renderer().type() == "categorizedSymbol":
        campo = renderer.legendClassificationAttribute()

        for cat in renderer.categories():
            if str(value) == cat.value():
                colorato = cat.symbol().symbolLayer(0).properties()['color']
                break
            
    return colorato

it is possible to capture the color and write it as an attribute of the layer itself:

to make elements of another layer acquire the same color following the proximity criterion, just use in the color property of the second layer, the expression:

overlay_nearest('Reg01012021_WGS84',"colore")[0]