diff --git a/chart.go b/chart.go
index d944882..5f0508d 100644
--- a/chart.go
+++ b/chart.go
@@ -315,6 +315,10 @@ func (c Chart) checkRanges(xr, yr, yra Range) error {
 		return errors.New("nan y-range delta")
 	}
 
+	if yDelta == 0 {
+		return errors.New("zero y-range delta")
+	}
+
 	if c.hasSecondarySeries() {
 		yraDelta := yra.GetDelta()
 		if math.IsInf(yraDelta, 0) {
@@ -323,6 +327,9 @@ func (c Chart) checkRanges(xr, yr, yra Range) error {
 		if math.IsNaN(yraDelta) {
 			return errors.New("nan secondary y-range delta")
 		}
+		if yraDelta == 0 {
+			return errors.New("zero secondary y-range delta")
+		}
 	}
 
 	return nil
diff --git a/defaults.go b/defaults.go
index 37bdc5a..13213fb 100644
--- a/defaults.go
+++ b/defaults.go
@@ -183,11 +183,6 @@ var (
 	DashArrayDashesLarge = []int{10, 10}
 )
 
-// NewColor returns a new color.
-func NewColor(r, g, b, a uint8) drawing.Color {
-	return drawing.Color{R: r, G: g, B: b, A: a}
-}
-
 // GetDefaultColor returns a color from the default list by index.
 // NOTE: the index will wrap around (using a modulo).
 func GetDefaultColor(index int) drawing.Color {