diff --git a/common/datatypes_test.go b/common/datatypes_test.go
new file mode 100644
index 0000000..4cc9702
--- /dev/null
+++ b/common/datatypes_test.go
@@ -0,0 +1,96 @@
+package common
+
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+)
+
+func TestColor_MarshalJSON(t *testing.T) {
+	c := Color(0)
+	var buf bytes.Buffer
+	if err := json.NewEncoder(&buf).Encode(c); err != nil {
+		t.Fatal(err)
+	}
+
+	if res := buf.String(); "\"#000000\"\n" != res {
+		t.Fatalf(`should be "#000000" but it's %#v'`, res)
+	}
+
+	buf.Reset()
+	c = Color(0xFFFFFF)
+	if err := json.NewEncoder(&buf).Encode(c); err != nil {
+		t.Fatal(err)
+	}
+
+	if res := buf.String(); "\"#ffffff\"\n" != res {
+		t.Fatalf(`should be "#ffffff" but it's %#v'`, res)
+	}
+
+	buf.Reset()
+	c = Color(0xFFFFFFFF)
+	if err := json.NewEncoder(&buf).Encode(c); err != nil {
+		t.Fatal(err)
+	}
+
+	if res := buf.String(); "\"#ffffff\"\n" != res {
+		t.Fatalf(`should be "#ffffff" but it's %#v'`, res)
+	}
+
+	buf.Reset()
+	cs := []Color{0xFF0000, 0x00FF00, 0x0000FF}
+
+	if err := json.NewEncoder(&buf).Encode(cs); err != nil {
+		t.Fatal(err)
+	}
+
+	if res := buf.String(); "[\"#ff0000\",\"#00ff00\",\"#0000ff\"]\n" != res {
+		t.Fatalf(`should be "["#ff0000","#00ff00","#0000ff"]" but it's %#v'`, res)
+	}
+}
+
+func TestColor_UnmarshalJSON(t *testing.T) {
+	val := `"#000000"`
+	var c Color
+	err := json.Unmarshal([]byte(val), &c)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if c != 0 {
+		t.Fatalf("should be 0, but its %x", c)
+	}
+
+	val = `"#ffffff"`
+	err = json.Unmarshal([]byte(val), &c)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if c != 0xffffff {
+		t.Fatalf("should be 0xffffff, but its %x", c)
+	}
+
+	vals := `["#ff0000", "#00ff00", "#0000ff"]`
+	cs := make([]Color, 0, 10)
+	err = json.Unmarshal([]byte(vals), &cs)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(cs) != 3 {
+		t.Fatalf("should be length of 3, but it's %d", len(cs))
+	}
+
+	if cs[0] != 0xFF0000 {
+		t.Fatalf("should be 0xFF0000, but it's %X", cs[0])
+	}
+
+	if cs[1] != 0x00FF00 {
+		t.Fatalf("should be 0x00FF00, but it's %X", cs[1])
+	}
+
+	if cs[2] != 0x0000FF {
+		t.Fatalf("should be 0x0000FF, but it's %X", cs[2])
+	}
+}