shared: add ColorItem from Gravity screensaver.

* A useful utility class that will also be used by Terminal later

Change-Id: I23020a401fbab7d4116df31f965ae61ecaf2a6cd

headers/private/shared/ColorItem.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2016-2022 Haiku, Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ *
+ * Authors:
+ *		John Scipione, [email protected]
+ *
+ * Based on ColorWhichItem by DarkWyrm ([email protected])
+ */
+#ifndef _COLOR_ITEM_H
+#define _COLOR_ITEM_H
+
+
+#include <InterfaceDefs.h>
+#include <StringItem.h>
+
+
+class ColorItem : public BStringItem {
+public:
+							ColorItem(const char* string, rgb_color color);
+
+	virtual	void			DrawItem(BView* owner, BRect frame, bool complete);
+			void			SetColor(rgb_color color) { fColor = color; }
+			rgb_color		Color() const { return fColor; }
+
+private:
+			rgb_color		fColor;
+};
+
+
+#endif	// _COLOR_ITEM_H