if you edit the color from the pallete directly, not just apply it then replace it, it should change all of them at once already, just click the tool to find it in the palette & modify it from there.

This also applies to alpha, edit it in the palette instead of the alpha slider & even that should take effect over all the icons in the same .dmi(icon) file.

-To modify things from the palette right click the color inside the palette which will bring up a window for color selection, includes a box to type in a value for alpha as well.

--Things may change for more things than you want, I haven't tested on frames of video & normal frames as well also possibly mixed in but if you have problems it changing more colors in things outside your animation you could always copy it to a new one as a whole then edit it from that icon file so it doesn't mess with others...

You can change colors in the entire icon inside the icon editor by using Colors > Edit from the file menu at the top. However, I don't think this can be used to swap alpha values.

If you're trying to make an entire icon transparent, this can be easily accomplished through just a few lines of code. You could also use SwapColor if you're only making a specific color transparent across the icon.