Create a button on your layout, apply a red fill colour to it, then apply conditional formatting on the button so that it changes the fill colour to green when the value of "viability" is 1.
Thank you for your attention, Nick, I guess that the solution it's nearly there but it involves a different procedures since I have to visualize a true image , inserted in a container, into the layout.
Thank you anyway for your effort.
> I have to visualize a true image , inserted in a container, into the layout.
To do that, you'll need three fields: a global container field for your red image (I'll call it Red_image), a global container field for your green image (Green_image) and a calculation field (Image_calculation) with the calculation result set to "container" .
Create a separate layout for your global container fields, then in Browse mode, insert your red and green images into the appropriate container fields.
Put the Image_calculation field on your main layout. The calculation for Image_calculation should look something like this:
Case ( Viability_field = "0" ; Red_image ; Viability_field = "1"; Green_image )
Hopefully, that should work!
Your instructions were perfect since also a newbie like me was able to achieve the result, thank you so much, Sir.