Inconsistency with categorical coloring using different cmaps

[Azaya89]

ALL software version info

Software Version Info

HoloViews = 1.20.1a0
bokeh = 3.6.2
matplotlib = 3.10.0

Description of expected behavior and the observed behavior

Expected behavior
I expect the colormaps in categorical plots to map to categories of the plot consistently

Observed behavior
Depending on the type of colormap used, the colors are parsed either linearly or categorically, sometimes even with the same type of colormap

Complete, minimal, self-contained example code that reproduces the issue

Some data

import pandas as pd, holoviews as hv, numpy as np

hv.extension('bokeh')
hv.opts.defaults(hv.opts.Points(width=400, height=300, xaxis=None, yaxis=None))

N_POINTS_PER_GROUP = 1_000
GRID_DIM = 3

data_frames = [
    pd.DataFrame({
        'x': np.random.normal(j, 0.25, N_POINTS_PER_GROUP),
        'y': np.random.normal(i, 0.25, N_POINTS_PER_GROUP),
        'cat': f'cat{GRID_DIM * i + j}'
    })
    for i in range(GRID_DIM) for j in range(GRID_DIM)
]

df = pd.concat(data_frames, ignore_index=True)

Using colorcet cmaps

import colorcet as cc

hv.Points(df, ['x', 'y']).opts(color='cat', cmap=cc.bwy) # a list of hex colors

Output
Colors are parsed linearly (Unexpected. Not ideal)

hv.Points(df, ['x', 'y']).opts(color='cat', cmap='bwy') # string value

Output
Colors are parsed categorically (Expected)

However, this passing of string names doesn't always work as expected:

hv.Points(df, ['x', 'y']).opts(color='cat', cmap='viridis')

Using bokeh color palette directly also doesn't work as expected

from bokeh.palettes import Viridis256 # a tuple of hex colors

hv.Points(df, ['x', 'y']).opts(color='cat', cmap=Viridis256)

Matplotlib ListedColormap works

from matplotlib import colormaps

hv.Points(df, ['x', 'y']).opts(color='cat', cmap=colormaps['viridis']) # ListedColormap object

Stack traceback and/or browser JavaScript console output

None

• I may be interested in making a pull request to address this

[ahuang11]

What if you set color_levels opts