diff --git a/src/Experimental.h b/src/Experimental.h
index 738d5e88b..32c609269 100755
--- a/src/Experimental.h
+++ b/src/Experimental.h
@@ -182,10 +182,16 @@
 #define EXPERIMENTAL_SCRUBBING_SCROLL_WHEEL
 
 // Paul Licameli (PRL) 24 May 2015
-// Allow scrolling up to one half of a screenful beyond either end of the project.
+// Allow scrolling up to one half of a screenful beyond either end of the project,
+// if you turn on the appropriate Tracks preference.
 // This allows smooth-scrolling scrub to work more reasonably at the ends.
 #define EXPERIMENTAL_SCROLLING_LIMITS
 
+// Paul Licameli (PRL) 28 May 2015
+// Draw negative numbers on the time ruler in a different color, when
+// scrolling past zero is enabled. Perhaps that lessens confusion.
+#define EXPERIMENTAL_TWO_TONE_TIME_RULER
+
 // Define to include crash reporting
 #define EXPERIMENTAL_CRASH_REPORT
 #if !defined(wxUSE_DEBUGREPORT) || !wxUSE_DEBUGREPORT
diff --git a/src/Project.cpp b/src/Project.cpp
index 6a8a32ccc..10ebf11f9 100755
--- a/src/Project.cpp
+++ b/src/Project.cpp
@@ -1096,7 +1096,7 @@ void AudacityProject::UpdatePrefs()
    }
 
    if (mRuler) {
-      mRuler->RegenerateTooltips();
+      mRuler->UpdatePrefs();
    }
 
    // The toolbars will be recreated, so make sure we don't leave
diff --git a/src/widgets/Ruler.cpp b/src/widgets/Ruler.cpp
index 69ba4d42d..496012014 100644
--- a/src/widgets/Ruler.cpp
+++ b/src/widgets/Ruler.cpp
@@ -54,6 +54,7 @@ array of Ruler::Label.
 *//******************************************************************/
 
 #include "../Audacity.h"
+#include "Ruler.h"
 
 #include <math.h>
 
@@ -68,7 +69,6 @@ array of Ruler::Label.
 #include "../AudioIO.h"
 #include "../Internat.h"
 #include "../Project.h"
-#include "Ruler.h"
 #include "../toolbars/ControlToolBar.h"
 #include "../Theme.h"
 #include "../AllThemeResources.h"
@@ -155,6 +155,8 @@ Ruler::Ruler()
    mGridLineLength = 0;
    mMajorGrid = false;
    mMinorGrid = false;
+
+   mTwoTone = false;
 }
 
 Ruler::~Ruler()
@@ -174,6 +176,11 @@ Ruler::~Ruler()
       delete[] mMinorMinorLabels;
 }
 
+void Ruler::SetTwoTone(bool twoTone)
+{
+   mTwoTone = twoTone;
+}
+
 void Ruler::SetFormat(RulerFormat format)
 {
    // IntFormat, RealFormat, RealLogFormat, TimeFormat, or LinearDBFormat
@@ -734,6 +741,7 @@ void Ruler::Tick(int pos, double d, bool major, bool minor)
    else
       label = &mMinorMinorLabels[mNumMinorMinor++];
 
+   label->value = d;
    label->pos = pos;
    label->lx = mLeft - 1000; // don't display
    label->ly = mTop - 1000;  // don't display
@@ -844,6 +852,7 @@ void Ruler::TickCustom(int labelIdx, bool major, bool minor)
    else
       label = &mMinorMinorLabels[labelIdx];
 
+   label->value = 0.0;
    pos = label->pos;         // already stored in label class
    l   = label->text;
    label->lx = mLeft - 1000; // don't display
@@ -1255,10 +1264,8 @@ void Ruler::Draw(wxDC& dc, TimeTrack* timetrack)
 
 #ifdef EXPERIMENTAL_THEMING
    mDC->SetPen(mPen);
-   mDC->SetTextForeground(mTickColour);
 #else
    mDC->SetPen(*wxBLACK_PEN);
-   mDC->SetTextForeground(*wxBLACK);
 #endif
 
    // Draws a long line the length of the ruler.
@@ -1316,10 +1323,7 @@ void Ruler::Draw(wxDC& dc, TimeTrack* timetrack)
          }
       }
 
-      if (mMajorLabels[i].text != wxT(""))
-         mDC->DrawText(mMajorLabels[i].text,
-                       mMajorLabels[i].lx,
-                       mMajorLabels[i].ly);
+      mMajorLabels[i].Draw(*mDC, mTwoTone);
    }
 
    if(mbMinor == true) {
@@ -1347,10 +1351,7 @@ void Ruler::Draw(wxDC& dc, TimeTrack* timetrack)
                                 mRight, mTop + pos);
             }
          }
-         if (mMinorLabels[i].text != wxT(""))
-            mDC->DrawText(mMinorLabels[i].text,
-                          mMinorLabels[i].lx,
-                          mMinorLabels[i].ly);
+         mMinorLabels[i].Draw(*mDC, mTwoTone);
       }
    }
 
@@ -1382,9 +1383,7 @@ void Ruler::Draw(wxDC& dc, TimeTrack* timetrack)
                                 mRight, mTop + pos);
             }
          }
-         mDC->DrawText(mMinorMinorLabels[i].text,
-                       mMinorMinorLabels[i].lx,
-                       mMinorMinorLabels[i].ly);
+         mMinorMinorLabels[i].Draw(*mDC, mTwoTone);
       }
    }
 }
@@ -1453,14 +1452,9 @@ int Ruler::FindZero(Label * label, const int len)
 {
    int i = 0;
    double d = 1.0;   // arbitrary
-   wxString s;
 
    do {
-      s = label[i].text;
-      if(!s.IsEmpty())
-         s.ToDouble(&d);
-      else
-         d = 1.0; // arbitrary, looking for some text here
+      d = label[i].value;
       i++;
    } while( (i < len) && (d != 0.0) );
 
@@ -1475,6 +1469,7 @@ int Ruler::GetZeroPosition()
    int zero;
    if((zero = FindZero(mMajorLabels, mNumMajor)) < 0)
       zero = FindZero(mMinorLabels, mNumMinor);
+   // PRL: don't consult minor minor??
    return zero;
 }
 
@@ -1527,6 +1522,22 @@ void Ruler::SetCustomMinorLabels(wxArrayString *label, int numLabel, int start,
    //Remember: delete majorlabels....
 }
 
+void Ruler::Label::Draw(wxDC&dc, bool twoTone) const
+{
+   if (text != wxT("")) {
+      bool altColor = twoTone && value < 0.0;
+
+#ifdef EXPERIMENTAL_THEMING
+      // TODO:  handle color distinction
+      mDC->SetTextForeground(mTickColour);
+#else
+      dc.SetTextForeground(altColor ? *wxBLUE : *wxBLACK);
+#endif
+
+      dc.DrawText(text, lx, ly);
+   }
+}
+
 //
 // RulerPanel
 //
@@ -1670,8 +1681,9 @@ AdornedRulerPanel::AdornedRulerPanel(wxWindow* parent,
    mPlayRegionDragsSelection = (gPrefs->Read(wxT("/QuickPlay/DragSelection"), 0L) == 1)? true : false; 
    mQuickPlayEnabled = gPrefs->Read(wxT("/QuickPlay/QuickPlayEnabled"), 1L); 
 
+   UpdatePrefs();
+
 #if wxUSE_TOOLTIPS
-   RegenerateTooltips();
    wxToolTip::Enable(true);
 #endif
 
@@ -1693,6 +1705,20 @@ AdornedRulerPanel::~AdornedRulerPanel()
       delete mSnapManager;
 }
 
+void AdornedRulerPanel::UpdatePrefs()
+{
+#ifdef EXPERIMENTAL_SCROLLING_LIMITS
+#ifdef EXPERIMENTAL_TWO_TONE_TIME_RULER
+   {
+      bool scrollBeyondZero = false;
+      gPrefs->Read(wxT("/GUI/ScrollBeyondZero"), &scrollBeyondZero, false);
+      ruler.SetTwoTone(scrollBeyondZero);
+   }
+#endif
+#endif
+   RegenerateTooltips();
+}
+
 void AdornedRulerPanel::RegenerateTooltips()
 {
 #if wxUSE_TOOLTIPS
diff --git a/src/widgets/Ruler.h b/src/widgets/Ruler.h
index 7a4f6a8e8..d1133f22d 100644
--- a/src/widgets/Ruler.h
+++ b/src/widgets/Ruler.h
@@ -60,6 +60,9 @@ class AUDACITY_DLL_API Ruler {
    // Optional Ruler Parameters
    //
 
+   // If twoTone is true, cause zero and positive numbers to appear black, negative in another color.
+   void SetTwoTone(bool twoTone);
+
    // IntFormat, RealFormat, or TimeFormat
    void SetFormat(RulerFormat format);
 
@@ -174,9 +177,12 @@ private:
 
    class Label {
     public:
+      double value;
       int pos;
       int lx, ly;
       wxString text;
+
+      void Draw(wxDC &dc, bool twoTone) const;
    };
 
    int          mNumMajor;
@@ -206,6 +212,7 @@ private:
    bool         mMinorGrid;      //         .
    int          mGridLineLength; //        end
    wxString     mUnits;
+   bool         mTwoTone;
 };
 
 class AUDACITY_DLL_API RulerPanel : public wxPanel {
@@ -269,6 +276,7 @@ public:
    void SetProject(AudacityProject* project) {mProject = project;};
    void GetMaxSize(wxCoord *width, wxCoord *height);
 
+   void UpdatePrefs();
    void RegenerateTooltips();
 
    bool mIsSnapped;