diff --git a/corrscope/gui/__init__.py b/corrscope/gui/__init__.py
index 2c8dd5b..2262425 100644
--- a/corrscope/gui/__init__.py
+++ b/corrscope/gui/__init__.py
@@ -494,6 +494,9 @@ class ShortcutButton(qw.QPushButton):
         self.setToolTip(keys.toString(QKeySequence.NativeText))
 
 
+# Begin ConfigModel properties
+
+
 def nrow_ncol_property(altered: str, unaltered: str) -> property:
     def get(self: "ConfigModel"):
         val = getattr(self.cfg.layout, altered)
@@ -541,6 +544,24 @@ def color2hex_property(path: str) -> property:
     return property(getter, setter)
 
 
+def color2hex_maybe_property(path: str) -> property:
+    # TODO turn into class, and use __set_name__ to determine assignment LHS=path.
+    def getter(self: "ConfigModel"):
+        color_attr = rgetattr(self.cfg, path)
+        if not color_attr:
+            return ""
+        return color2hex(color_attr)
+
+    def setter(self: "ConfigModel", val: str):
+        if val:
+            color = color2hex(val)
+        else:
+            color = None
+        rsetattr(self.cfg, path, color)
+
+    return property(getter, setter)
+
+
 def path_strip_quotes(path: str) -> str:
     if len(path) and path[0] == path[-1] == '"':
         return path[1:-1]
@@ -569,6 +590,7 @@ class ConfigModel(PresentationModel):
 
     render__bg_color = color2hex_property("render__bg_color")
     render__init_line_color = color2hex_property("render__init_line_color")
+    render__grid_color = color2hex_maybe_property("render__grid_color")
 
     @property
     def render_video_size(self) -> str:
@@ -603,6 +625,9 @@ class ConfigModel(PresentationModel):
     render__line_width = default_property("render__line_width", 1.5)
 
 
+# End ConfigModel
+
+
 class ChannelTableView(qw.QTableView):
     def append_channels(self, wavs: List[str]):
         model: ChannelModel = self.model()
diff --git a/corrscope/gui/mainwindow.ui b/corrscope/gui/mainwindow.ui
index 521d9c1..86e4167 100644
--- a/corrscope/gui/mainwindow.ui
+++ b/corrscope/gui/mainwindow.ui
@@ -167,6 +167,16 @@
              </property>
             </widget>
            </item>
+           <item row="3" column="0">
+            <widget class="QLabel" name="render__grid_colorL">
+             <property name="text">
+              <string>Grid Color</string>
+             </property>
+            </widget>
+           </item>
+           <item row="3" column="1">
+            <widget class="BoundLineEdit" name="render__grid_color"/>
+           </item>
           </layout>
          </widget>
         </item>
diff --git a/corrscope/layout.py b/corrscope/layout.py
index ce4765e..2a01391 100644
--- a/corrscope/layout.py
+++ b/corrscope/layout.py
@@ -1,4 +1,4 @@
-from typing import Optional, TypeVar, Callable, List
+from typing import Optional, TypeVar, Callable, List, Generic
 
 import numpy as np
 
@@ -92,3 +92,11 @@ class RendererLayout:
             regions2d = regions2d.T
 
         return regions2d.flatten()[: self.nplots].tolist()
+
+
+class EdgeFinder(Generic[Region]):
+    def __init__(self, regions2d: np.ndarray):
+        self.tops: List[Region] = regions2d[0, :].tolist()
+        self.bottoms: List[Region] = regions2d[-1, :].tolist()
+        self.lefts: List[Region] = regions2d[:, 0].tolist()
+        self.rights: List[Region] = regions2d[:, -1].tolist()
diff --git a/corrscope/renderer.py b/corrscope/renderer.py
index 41d4b7e..3a07f92 100644
--- a/corrscope/renderer.py
+++ b/corrscope/renderer.py
@@ -7,7 +7,7 @@ import numpy as np
 import attr
 
 from corrscope.config import register_config
-from corrscope.layout import RendererLayout, LayoutConfig
+from corrscope.layout import RendererLayout, LayoutConfig, EdgeFinder
 from corrscope.outputs import RGB_DEPTH, ByteBuffer
 from corrscope.util import coalesce
 
@@ -60,6 +60,7 @@ class RendererConfig:
 
     bg_color: str = "#000000"
     init_line_color: str = default_color()
+    grid_color: Optional[str] = None
 
 
 @attr.dataclass
@@ -137,6 +138,8 @@ class MatplotlibRenderer(Renderer):
 
         self._set_layout()  # mutates self
 
+    transparent = "#00000000"
+
     def _set_layout(self) -> None:
         """
         Creates a flat array of Matplotlib Axes, with the new layout.
@@ -152,18 +155,50 @@ class MatplotlibRenderer(Renderer):
             raise Exception("I don't currently expect to call _set_layout() twice")
             # plt.close(self.fig)
 
+        grid_color = self.cfg.grid_color
         axes2d: np.ndarray["Axes"]
         self._fig, axes2d = plt.subplots(
             self.layout.nrows,
             self.layout.ncols,
             squeeze=False,
-            # Remove gaps between Axes
+            # Remove axis ticks (which slow down rendering)
+            subplot_kw=dict(xticks=[], yticks=[]),
+            # Remove gaps between Axes TODO borders shouldn't be half-visible
             gridspec_kw=dict(left=0, bottom=0, right=1, top=1, wspace=0, hspace=0),
         )
 
-        # remove Axis from Axes
-        for ax in axes2d.flatten():
-            ax.set_axis_off()
+        ax: "Axes"
+        if grid_color:
+            # Initialize borders
+            for ax in axes2d.flatten():
+                # Hide Axises
+                # (drawing them is very slow, and we disable ticks+labels anyway)
+                ax.get_xaxis().set_visible(False)
+                ax.get_yaxis().set_visible(False)
+
+                # Background color
+                ax.set_facecolor(self.transparent)
+
+                # Set border colors
+                for spine in ax.spines.values():
+                    spine.set_color(grid_color)
+
+                # gridspec_kw indexes from bottom-left corner.
+                # Only show bottom-left borders (x=0, y=0)
+                ax.spines["top"].set_visible(False)
+                ax.spines["right"].set_visible(False)
+
+            # Hide bottom-left edges for speed.
+            edge_axes: EdgeFinder["Axes"] = EdgeFinder(axes2d)
+            for ax in edge_axes.bottoms:
+                ax.spines["bottom"].set_visible(False)
+            for ax in edge_axes.lefts:
+                ax.spines["left"].set_visible(False)
+
+        else:
+            # Remove Axis from Axes
+            for ax in axes2d.flatten():
+                ax.set_axis_off()
 
         # Generate arrangement (using nplots, cfg.orientation)
         self._axes = self.layout.arrange(lambda row, col: axes2d[row, col])