diff --git a/ordinary/ordinary.go b/ordinary/ordinary.go
index 6f34a0e..321c0d0 100644
--- a/ordinary/ordinary.go
+++ b/ordinary/ordinary.go
@@ -446,14 +446,24 @@ func (variogram *Variogram) Plot(gridMatrices *GridMatrices, width, height int,
 			} else {
 				x := float64(width) * (float64(i)*gridMatrices.Width + gridMatrices.Xlim[0] - xlim[0]) / range_[0]
 				y := float64(height) * (1 - (float64(j)*gridMatrices.Width+gridMatrices.Ylim[0]-ylim[0])/range_[1])
-				z := (gridMatrices.Data[i][j] - gridMatrices.Zlim[0]) / range_[2]
+				distance := gridMatrices.Data[i][j] - gridMatrices.Zlim[0]
+				z := (distance) / range_[2]
 				if z < 0 {
 					z = 0.0
 				} else if z > 1 {
 					z = 1.0
 				}
 
-				colorIndex := int(math.Floor((float64(len(colors)) - 1) * z))
+				colorIndex := -1
+				for index, item := range colors {
+					if distance >= item.Value[0] && distance <= item.Value[1] {
+						colorIndex = index
+						break
+					}
+				}
+				if colorIndex == -1 {
+					continue
+				}
 				color := colors[colorIndex].Color
 				ctx.DrawRect(math.Round(x-wx/2), math.Round(y-wy/2), wx, wy, color)
 			}
diff --git a/ordinary/type.go b/ordinary/type.go
index 5efcecb..e56af5d 100644
--- a/ordinary/type.go
+++ b/ordinary/type.go
@@ -32,6 +32,7 @@ var (
 		{Color: NewRGBA(250, 250, 100, 255), Value: [2]float64{5, 10}},
 		{Color: NewRGBA(252, 207, 81, 255), Value: [2]float64{10, 15}},
 		{Color: NewRGBA(252, 164, 63, 255), Value: [2]float64{15, 20}},
+		{Color: NewRGBA(247, 122, 45, 255), Value: [2]float64{20, 25}},
 		{Color: NewRGBA(242, 77, 31, 255), Value: [2]float64{25, 30}},
 		{Color: NewRGBA(232, 16, 20, 255), Value: [2]float64{30, 40}},
 	}
@@ -72,14 +73,14 @@ type ContourRectangle struct {
 	YResolution float64    `json:"yResolution"`
 }
 
-type Point [2]float64 // [103.614373, 27.00541]
+type Point [2]float64 // example [103.614373, 27.00541]
 
-type Ring []Point // [[103.614373, 27.00541],[104.174357, 26.635252],[104.356163, 28.018448],[103.614373, 27.00541]]
+type Ring []Point
 
-type PolygonCoordinates []Ring // [[[103.614373, 27.00541],[104.174357, 26.635252],[104.356163, 28.018448],[103.614373, 27.00541]]]
+type PolygonCoordinates []Ring
 
 type PolygonGeometry struct {
-	Type        string `json:"type" example:"Polygon"` // Polygon
+	Type        string `json:"type" default:"Polygon"` // Polygon
 	Coordinates []Ring `json:"coordinates,omitempty"`  // coordinates
 }
 
@@ -89,6 +90,6 @@ func NewRGBA(r, g, b, a uint8) color.RGBA {
 }
 
 type GridLevelColor struct {
-	Value [2]float64 `json:"value" example:"0,5"` // [0, 5]
-	Color color.RGBA `json:"color"`               // {255, 255, 255, 255}
+	Value [2]float64 `json:"value"` // 值区间 [0, 5]
+	Color color.RGBA `json:"color"` // RGBA颜色 {255, 255, 255, 255}
 }