Color() Troubles

I can't seem to grasp how Color works in C#. I'm trying to darken a sprite when night falls, using SpriteManager. SpriteManager is changing the colors (I can get a black sprite, or a blue sprite, red sprite, green sprite, etc).

For debug purposes I am using a gray scale sprite, and I'm attempting to color it light blue or dark navy blue depending on time... It doesn't seem to work though.

 if (_night & _transition)
             {
                 Color _color = new Vector4(17f, 55f, 74f, 255f).normalized;
                 Main.level.skySprite.SetColor(_color);
                 _transition = false;
             }
 
 if (_day & _transition)
             {
                 Color _color = new Vector4(205f, 227f, 238f, 255f).normalized;
                 Main.level.skySprite.SetColor(_color);
                 _transition = false;
             }