feat: added colors parameter to allow user to select the colour of ea…

…ch histogram

src/mplhep/plot.py

@@ -4,7 +4,7 @@
 import inspect
 import warnings
 from collections import OrderedDict, namedtuple
-from typing import TYPE_CHECKING, Any, Union
+from typing import TYPE_CHECKING, Any, Union, List
 
 import matplotlib as mpl
 import matplotlib.pyplot as plt
@@ -68,6 +68,7 @@ def histplot(
     histtype="step",
     xerr=False,
     label=None,
+    colors=None,
     sort=None,
     edges=True,
     binticks=False,
@@ -125,6 +126,8 @@ def histplot(
             Size of xerr if ``histtype == 'errorbar'``. If ``True``, bin-width will be used.
         label : str or list, optional
             Label for legend entry.
+        colors : any valid mpl color or iterable thereof, optional
+            The color for each histogram
         sort: {'label'/'l', 'yield'/'y'}, optional
             Append '_r' for reverse.
         edges : bool, default: True, optional
@@ -296,6 +299,16 @@ def histplot(
     else:
         _labels = [str(lab) for lab in label]
 
+    _colors: List
+    if colors is None:
+        _colors = [None] * len(plottables)
+    elif isinstance(colors, str):
+        _colors = [colors] * len(plottables)
+    elif not np.iterable(colors):
+        _colors = [str(colors)] * len(plottables)
+    else:
+        _colors = colors
+
     def iterable_not_string(arg):
         return isinstance(arg, collections.abc.Iterable) and not isinstance(arg, str)
 
@@ -425,6 +438,8 @@ def iterable_not_string(arg):
 
             _plot_info = plottables[i].to_stairs()
             _plot_info["baseline"] = None if not edges else 0
+            if _colors[i] is not None:
+                _plot_info["color"] = _colors[i]
             _s = ax.stairs(
                 **_plot_info,
                 label=_step_label,
@@ -454,8 +469,11 @@ def iterable_not_string(arg):
     elif histtype == "fill":
         for i in range(len(plottables)):
             _kwargs = _chunked_kwargs[i]
+            _plot_info = {}
+            if _colors[i] is not None:
+                _plot_info["color"] = _colors[i]
             _f = ax.stairs(
-                **plottables[i].to_stairs(), label=_labels[i], fill=True, **_kwargs
+                **_plot_info, **plottables[i].to_stairs(), label=_labels[i], fill=True, **_kwargs
             )
             return_artists.append(StairsArtists(_f, None, None))
         _artist = _f
@@ -482,6 +500,8 @@ def iterable_not_string(arg):
             if yerr is False:
                 _plot_info["yerr"] = None
             _plot_info["xerr"] = _xerr
+            if _colors[i] is not None:
+                _plot_info["color"] = _colors[i]
             _e = ax.errorbar(
                 **_plot_info,
                 label=_labels[i],

tests/test_basic.py

@@ -562,3 +562,17 @@ def test_histplot_inputs_pass(h, yerr, htype):
     fig, ax = plt.subplots()
     hep.histplot(h, bins, yerr=yerr, histtype=htype)
     plt.close(fig)
+
+
+@pytest.mark.mpl_image_compare(style="default", remove_text=True)
+def test_color():
+    hs, bins = [[2, 3, 4], [5, 4, 3]], [0, 1, 2, 3]
+    fig, axs = plt.subplots(3, 2, figsize=(8, 12))
+    colors = ['green', 'blue']
+    axs = axs.flatten()
+
+    for i, htype in enumerate(["step", "fill", "errorbar"]):
+        hep.histplot(hs[0], bins, yerr=True, histtype=htype, ax=axs[i * 2], alpha=0.7, color='red')
+        hep.histplot(hs, bins, yerr=True, histtype=htype, ax=axs[i * 2 + 1], alpha=0.7, color=colors)
+
+    return fig