@asdrgil Is this what you are looking for?. I have removed leading zeros from the number to make it easy to read.
d = {'index':[1,2,3,4],
'start':[23,53,71,91],
'end':[5300000,7100000,9100000,12500000],
'bar_len':[30,18,20,34],
'name':['p36.32','p36.31','p36.23','p36.22'],
'color':['#949494','#FFFFFF','#949494','#FFFFFF'],
'gr':['g1','g1','g1','g1']}
df = pd.DataFrame(d)
df_melt = df.melt(id_vars=['start','color'], value_vars=['bar_len'])
fig = px.bar(df_melt, y='start', x='value', color='color', orientation='h')
fig.update_yaxes(type='category')
fig.show()
