How can I customized border of go.Choroplethmapbox

I use this code to display map. I want to ask:

  • How can I change border to inner area.
  • Different color for different area (for example: yellow border for yellow area and dark green border for green area).
import json
from urllib.request import urlopen
with urlopen('') as response:
    counties = json.load(response)

import pandas as pd
df = pd.read_csv("",
                   dtype={"fips": str})

import plotly.graph_objects as go

fig = go.Figure(go.Choroplethmapbox(geojson=counties, locations=df.fips, z=df.unemp,
                                    colorscale="Viridis", zmin=0, zmax=12,
                                    marker_opacity=0.5, marker_line_width=2))
                  mapbox_zoom=3, mapbox_center = {"lat": 37.0902, "lon": -95.7129})