Hi, depending on how you open the file, initial visualization may change: for some kind of file format you can choose to visualize directly many channel as "Composite" (different channel merged), otherwise could have different channels separated; in this case you should use "Image/Color/Merge Channels..." from drop-down menu.
Instead, if you are interested in see you DAPI and TRITC channel separated, but you want play them at the same time, you could put one beside the other with "Image/Stacks/Tools/Combine...".
Hope this can help you,
best regards,
Rocco
Senior Microscopist
Crick Advanced Light Microscopy facility (CALM)
The Francis Crick Institute
1 Midland Road, NW1 1AT, London (UK)
https://roccodant.github.io/