How to use the same filament for 2 colors of 4 color print?

I've got a 3ml file that uses light blue for eyes and regular blue for the main body and I would like to use regular blue for both the eyes and body as I don't have light blue filament and it should cut down on filament changes in print time.

The problem is I can't figure out how to tell it to do this before I slice the plate and Bambu Studio. I know I can select the same filament for both colors when I click print plate. I'm concerned that won't actually reduce the print time or the number of filament changes though since that is a change I'm making after it is sliced and therefore. Is that a correct assumption? If so, how do I fix this before I slice it? I can't seem to select the exact same color for two of the four filaments in the project filaments area on the left side of Studio in prepare mode even though that seems like the right place to make the change. Thanks for your help.