Add color functions

grey and alpha

framer/Color.coffee

@@ -153,16 +153,22 @@ class exports.Color extends BaseClass
	toString: ->
		return @toRgbString()

	transparent: ->
	alpha: (alpha = 1) ->
		result = new Color
			r: @r
			g: @g
			b: @b
			a: 0
			a: alpha

	transparent: ->
		@alpha(0)

	mix: (colorB, fraction, limit = false, model) ->
		return Color.mix(@, colorB, fraction, limit, model)

	copy: ->
		return new Color(@)

	isEqual: (colorB) ->
		return Color.equal(@, colorB)

@@ -254,6 +260,12 @@ class exports.Color extends BaseClass
		c = -> parseInt(Math.random() * 255)
		return new Color "rgba(#{c()}, #{c()}, #{c()}, #{alpha})"

	@grey: (g = 0.5, alpha = 1) ->
		g = parseInt(g * 255)
		return new Color "rgba(#{g}, #{g}, #{g}, #{alpha})"

	@gray: (args...) -> @grey(args...)

	@toColor: (color) -> return new Color(color)
	@validColorValue: (color) -> return color instanceof Color or color == null