[Python] Colouring a surface using Mesh3d in python plotly

I would aim to colour a surface in a 3D plot, created using plotly.graph_objects.

I worked on an approach incorporating Mesh3d, the code runs, but the wanted surface is still not coloured. What is the mistake I made, or should another approach be used?

The final outcome is desired to look similar to this 3D plot:

And this is where I am at now (I don't aim to apply color scaling to the surface, it is good enough to be filled with a consistent colour):

So, the aim would be to colour the surface where the vertical lines are connecting the two curves (2D and the same in 3D).

Here is my code:

import plotly.graph_objects as go
import numpy as np

def plot_3d_course_profile(x, y, z, color_attribute, colorbar_label):
fig = go.Figure()

# Bottom curve at altitude = 350
fig.add_trace(go.Scatter3d(
x=x,
y=y,
z=[350] * len(x),
mode='lines',
line=dict(
color='black',
width=5,
)
))

# Profile curve
fig.add_trace(go.Scatter3d(
x=x,
y=y,
z=z,
mode='lines',
line=dict(
color=color_attribute,
width=13,
colorscale='Jet',
colorbar=dict(
title=dict(
text=colorbar_label,
font=dict(size=14, color='black')
),
thickness=20,
len=0.6,
tickfont=dict(size=12, color='black'),
tickmode='linear',
tickformat='.2f',
outlinewidth=1,
outlinecolor='black'
)
)
))

# Vertical lines
for i in range(0, len(x), 7):
xi, yi, zi = x, y, z
fig.add_trace(go.Scatter3d(
x=[xi, xi],
y=[yi, yi],
z=[350, zi],
mode='lines',
line=dict(color='dimgray', width=4),
opacity=0.6,
showlegend=False
))

# surface - not displaying
fig.add_trace(go.Mesh3d(
x=np.concatenate([x, x[::-1]]),
y=np.concatenate([y, y[::-1]]),
z=np.concatenate([[350] * len(x), z[::-1]]),
color='blue',
opacity=0.5,
showscale=False
))

fig.update_layout(
template='plotly_white',
scene=dict(
xaxis=dict(title='Meters north from start position', showgrid=True, gridcolor='lightblue', zeroline=False),
yaxis=dict(title='Meters east from start position', showgrid=True, gridcolor='lightblue', zeroline=False),
zaxis=dict(title='Altitude [m]', showgrid=True, gridcolor='lightblue', zeroline=False),
aspectmode='manual',
aspectratio=dict(x=1.25, y=1, z=0.7)
),
title=f'3D Course Profile Colored by {colorbar_label}',
margin=dict(l=0, r=0, b=0, t=50)
)

fig.show()

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