I'm using dash to create company compliant graphs so I'm using a custom ste of colors that are provided by the communication team in a company mini-package. I get them as hex colors.

I would like to create a "in between" and thus change the alpha channel of my color to make half transparent.

As in this plotting:

import plotly.graph_objects as go
from matplotlib.colors import to_rgb

color = "#4E9D2D"

fig = go.Figure()
fig.add_trace(go.Scatter(x=[1, 2, 3, 4], y=[3, 4, 8, 3],
    fill=None,
    mode='lines',
    line = {"width": 0},
    ))
fig.add_trace(go.Scatter(
    x=[1, 2, 3, 4],
    y=[1, 6, 2, 6],
    fill='tonexty',
    mode='lines',
    line = {"width": 0},
    fillcolor=f"rgba({','.join([str(int(c*255)) for c in to_rgb(color)])}, .1)"
))

fig.show()

Currently color specifier are supporting:

• A hex string (e.g. '#ff0000')
• An rgb/rgba string (e.g. 'rgb(255,0,0)')
• An hsl/hsla string (e.g. 'hsl(0,100%,50%)')
• An hsv/hsva string (e.g. 'hsv(0,100%,100%)')
• A named CSS color

In my use case that forces me to use this horrible line to create the half transparent color in rgba:

f"rgba({','.join([str(int(c*255)) for c in to_rgb(color)])}, .1)"

I cannot rely on the to_rgba function becasue you expect the 3 first digit to be int between 0 and 255 and the alpha channel as float when the matplotlib standard is giving me everything as a float.

What I would love to do is being allowed to add 2 extra digit to my hex chain to provide the alpha channel as :

color = f"{color}1a"

It's compatible with the other plotting tools I'm using (bokeh and matplotlib) but not with yours could you add the support for it ?