Summary

Fixes#5416.

You can define color sequences in a template on a per-trace basis viatemplate.data.<trace_type>, but these were ignored by Plotly Express. Now they are used.

Changes

• Modifiedapply_default_cascade() to check for trace-specific colors intemplate.data.<trace_type> before falling back totemplate.layout.colorway or default qualitative palette
• Addedtest_px_templates_trace_specific_colors

Example Usage

See here for a demonstration of all (I think?) applicable trace types, i.e. those that supportmarker.color.

importplotly.expressaspximportplotly.graph_objectsasgotips=px.data.tips()# Create a custom template with trace-specific colorscustom_template=go.layout.Template(data={"histogram": [go.Histogram(marker=dict(color="orange")),go.Histogram(marker=dict(color="purple")),        ],"scatter": [go.Scatter(marker=dict(color="cyan")),go.Scatter(marker=dict(color="magenta")),        ],    },layout=go.Layout(colorway=["yellow","green"]),)template=pio.templates.merge_templates("plotly",custom_template)# Histogram uses histogram-specific colorsfig1=px.histogram(tips,x="total_bill",color="sex",template=template)# Scatter uses scatter-specific colorsfig2=px.scatter(tips,x="total_bill",y="tip",color="sex",template=template)# Box plot falls back to layout.colorwayfig3=px.box(tips,x="day",y="total_bill",color="sex",template=template)

Code PR

• I have read through thecontributing notes and understand the structure of the package. In particular, if my PR modifies code ofplotly.graph_objects, my modifications concern the code generator andnot the generated files.
• I have added tests or modified existing tests.
• For a new feature, I have added documentation examples (please see the doc checklist as well).
• I have added a CHANGELOG entry if changing anything substantial.
• For a new feature or a change in behavior, I have updated the relevant docstrings in the code.