Add CHANGELOG entry for trace-specific color sequences fix

Author: antonymilne

CHANGELOG.md

@@ -4,6 +4,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+### Fixed
+- Fix issue where Plotly Express ignored trace-specific color sequences defined in templates via `template.data.<trace_type>`. Plotly Express now respects trace-specific marker colors before falling back to `template.layout.colorway` [[#5437](https://github.com/plotly/plotly.py/pull/5437)]. Fixes [#5416](https://github.com/plotly/plotly.py/issues/5416).
+
 ### Updated
 - Speed up `validate_gantt` function [[#5386](https://github.com/plotly/plotly.py/pull/5386)], with thanks to @misrasaurabh1 for the contribution!