If you want the field to always display green text, click on the field in layout mode, then on the Appearance tab in the Inspector, under text, change the color.
Or, do you want something like a conditional formatting calculation that will make the text green if its a credit, and red if its a debit?
And there are different ways to compute a "sum total" depending on the design of your layout. You can sum different fields within the same record, the same field across a set of records in a related table (which might be shown in a portal) or across a found set of records on your layout.
What I want to be able to do is, "Sum" the text that are green (in colour) text only, not "Sum" the text that are black (in colour) . Is this possible.
It is possible, but not simple. There are functions that can detect the text color.
What action chooses the color of the text?
Is this text that includes many other characters besides just the number? Multiple entries in the same field? or ???
And as noted in my last post, how you sum anything in FileMaker will depend in part on your database design. Are these all fields in one record, a single field in multiple records? Do you need to see this from the context of a related parent record? (In other words, are you summing data shown in a portal?)