There can be a few reasons for this.
The field is simply not available for write back via AOI
When users create a new AOI template be that a customer record, supplier record, projects etc. The field I want to write back does not allow them to do that is be design.
Not all fields that can be edited in the Dimensions or Financials front can be changed via AOI. Those that can are displayed with the values being presented with blue text and those which cannot, presented in black.
The most common reason for a field not being available for changed in AOI is because the user would be prompted to select the data in the finance front end to ensure a valid value is selected.
Setting to allow data to be written back to Access Accounts not selected
The user has edit permissions (see below) in Dimensions or Financials but has not selected to 'Allow change to be written back to Access Accounts' option on the last step of the template creation. At which point none of the fields will be displayed in blue (as noted above).
The template can be edited and the option selected and reinserted at which point any fields that can be written back with be displayed in blue.
Security profile restrictions
A security profile can define if a specific user is able to edit in the finance application itself and as a result, if they are not allowed to edit customers (for example) in their finance application, then they will not be able to edit via AOI.