I've observed problems with some of the blend modes in Fireworks CS5 and CS6. Several are definitely broken—most likely a by-product of changes introduced in CS5, which attempted to match some of Photoshop's blend mode behaviors (for Hue, Saturation, Color and Luminosity).
The broken blend modes are the channel-based blend modes: Red, Green, and Blue. These have no counterpart in Photoshop, and yet no longer function properly.
To illustrate the problem, I've created a simple test graphic: three white squares, three black squares, three bitmaps, and three colored squares (red, green, and blue).
Now I'll add a black background to the canvas and apply a different channel-based blend mode—Red, Green, and Blue—to each object in its respective group. Here's the correct result, in Fireworks 8:
As you can see, each object appears to be the same color as its applied blend mode. A white rectangle with a Red blend mode becomes red, with a Green blend mode becomes green, and with a Blue blend mode becomes blue.
The way it works is this: The composite image adopts the selected channel of the object and combines it with the remaining channels of the canvas (or objects) below. For example, consider the white rectangle with a Red blend mode. The rectangle's Red channel (R:255) should be combined with the remaining channels of the canvas below (G:0,B:0) to create a composite with the appearance of red (R:255,G:0,B:0).
Now here's the same graphic as it appears in both Fireworks CS5 and CS6:
As you can see, there's no sense to this result. The Red blend mode produces Green, the Green blend mode produces Red, and the Blue blend mode produces invisibility. I simply cannot explain the outcome. These blend modes have been rendered useless and unintelligible in CS5 and CS6.
The reason for my concern here is that, just over a year ago, I wrote a series of command scripts based on these blend modes as they existed Fireworks 8. Without these blend modes, my scripts cannot function.
Assuming there are updates forthcoming for Fireworks CS6, I'm hoping there's a chance that this might still be fixed (if not for CS5, as well). Here's the bug report I've submitted regarding this issue:
Product name: Fireworks
Product Version: 188.8.131.52 (CS5.1)/184.108.40.206 (CS6)
Product Language: English
Your operating system: OS 10.6.8
Concise problem statement: Channel-based blend modes (Red, Green, and Blue) are broken in Fireworks CS6 and CS5.
Steps to reproduce bug:
1. Set canvas to black.
2. Draw 3 white rectangles of any size.
3. Set blend mode of 1st rectangle to Red, 2nd rectangle to Green, 3rd rectangle to Blue.
Results: 1st rectangle appears Green (instead of Red). 2nd rectangle appears Red (instead of Green). 3rd rectangle becomes invisible (instead of Blue).
Expected results: Each rectangle should appear to be the same color as its applied blend mode, as the composite adopts the selected channel of the object and combines it with the remaining channels of the canvas (or objects) below.
In the preceding example, the black canvas contains no channel information (R:0,G:0,B:0) while the white rectangles contain information in all 3 channels (R:255,G:255,B:255). When a Red blend mode is applied to a white rectangle, the object's Red channel (R:255) should be combined with the remaining channels of the canvas below (G:0,B:0) to create a composite with the appearance of red (R:255,G:0,B:0).
Most likely, this bug was introduced in CS5, which included modifications to Hue, Saturation, Color and Luminosity blend modes (to match Photoshop). For comparison, proper RGB blend mode behavior was observed in Fireworks 8.
For more information about this bug, please see the following post: http://forums.adobe.com/thread/1209542