I have the following data:
import numpy as np
from scipy import stats
import plotly.graph_objects as go
# Simlate Random Walk
N = 100
xs = np.arange(N)
X = np.zeros(N)
for i in range(1, N):
X[i] = X[i1] + np.random.normal(scale=1)
# Measurements
Y = X + np.random.normal(scale=1, size=N)
# Moving average over the measurements
Z = np.column_stack([Y[:3],Y[3:]]).mean(axis=1)
# Quantiles
lower, upper = stats.norm.ppf([.025, .975], loc=Z[:,None], scale=1).T
Plotting:
fig = go.Figure()
fig.add_scatter(x=xs, y=X)
fig.add_scatter(x=xs, y=Y, mode='markers')
fig.add_scatter(x=xs[3:], y=Z, line_shape='spline')
fig.add_scatter(x=np.concatenate([xs[3:],xs[3:][::1]]), y=np.concatenate([lower, upper[::1]]),
fill='toself', line_width=0)
fig.layout.update(height=600, showlegend=False)
fig.show()
The filling covers the other plots, I want to send it to the background, that is, as if it were the first trace to be added without changing the colors of any of the traces.
If I were to simply add this trace first, all my feng shui would be distorted, colors will no longer correspond to those already used to create previous plots.
Some solutions would be:

always use my own colors. A pity, I like the ones
plotly
provides but I cannot retrieve them.
(Related to: Get color of a trace) 
keep the colors as they are, but change the order of traces. This I do not know how to do and is the subject of this question.
Another motivation, is that I want to be able to hover over some of the covered traces.
I have asked here about that: