In this Macromedia Flash tutorial I will show you how to make a stylish colored image / black and white masking animation effect.

1.
I started with a colorful flower image opened up my photoshop and made a black and white image so I had both a colored one and one in black and white, with the excact same width and heights.

Then import them both to the stage in Flash
file -> import -> import to stage

2.
Now place the two images center of the stage, and put them in to seperate layers.
Place the black and white layer at the bottem and click the lock handle at the left in the layers panel to lock it.

3.
Now make a new layer at the top in the layers panel and name it mask, draw a black square as shown in the image below.
Right click it and convert it to a movie clip.

4.
Now in the timeline for each layer create a new keyframe at frame 40, then create one at frame 20.
Go to frame 20 and drag the black mask square all the way to the other side.

5.
Now right click between frame 1 and 20 and choose create motion tween, do the same between frame 20 and 40.

6.
Now right click in the layers panel on the layer called mask, and choose mask.

Now test your movie and you should have accomplished my effect.