title: Can alpha transparency fill or stroke style be set separately from RGB in Canvas HTML5?
body: <p>In Canvas/HTML5, I know you can use RGBA to set color and alpha transparency for fillStyle or strokeStyle.  You can also use just RGB to set color with no alpha channel.  is there a way you can change the alpha value of an item without also supplying the color.</p>
  
  <p>My example would be wanting to change the fillStyle or strokeStyle above a canvas section whose color was random or no longer known.  Is there a way to change the alpha through another attribute or by passing nothing to the color (e.g. ctx.fillStyle = 'rgba(,,,alphaValue)';)</p>