Why I can't save multiple channels, multiple slices as a single Tiff file to view it with any viewer

I noticed this problem is when I combine multiple channel Tiffs into one and save them as one file. The file saved when I open it with any viewer, I see all as red channel

path = "...";

run("Merge Channels...", "c1=red.tif c2=green.tif create");
run("Channels Tool...");

saveAs("Tiff", path+"Composite.tif");

red.tif (3.0 MB)
green.tif (3.0 MB)
Composite.tif (3.0 MB)

I found a solution by converting it to RGB but this only worked having one slice but not more than that.

selectWindow("Composite"); // 3MB
run("Channels Tool...");
run("Stack to RGB"); // 12 MB
saveAs("Tiff", path+"Composite(RGB).tif");

Composite.tif (6.0 MB)

Any help how to save the image and view it properly is appreciated.

It might be that it is answered in that post
checking to confirm…