diff --git a/lib/Color.ts b/lib/Color.ts
index 778338d..d47c855 100644
--- a/lib/Color.ts
+++ b/lib/Color.ts
@@ -13,10 +13,10 @@ export class Color {
   public static readonly transparent = new Color (0, 0, 0, 0);
   public static readonly gray = new Color (128, 128, 128);
 
-  private red: number;
-  private green: number;
-  private blue: number;
-  private alpha: number;
+  private _red: number;
+  private _green: number;
+  private _blue: number;
+  private _alpha: number;
 
   private check_range (n: number): void {
     if (n < 0 || n > 255)
@@ -28,25 +28,25 @@ export class Color {
     this.check_range (green);
     this.check_range (blue);
     this.check_range (alpha);
-    this.red = red;
-    this.green = green;
-    this.blue = blue;
-    this.alpha = alpha;
+    this._red = red;
+    this._green = green;
+    this._blue = blue;
+    this._alpha = alpha;
   }
 
   // eslint-disable-next-line @typescript-eslint/naming-convention
   public toString (): string {
     return `#${num_to_hex (
-      this.red,
+      this._red,
       2
     )}${num_to_hex (
-      this.green,
+      this._green,
       2
     )}${num_to_hex (
-      this.blue,
+      this._blue,
       2
-    )}${this.alpha === 255
+    )}${this._alpha === 255
       ? ''
-      : num_to_hex (this.alpha, 2)}`;
+      : num_to_hex (this._alpha, 2)}`;
   }
 }