Gray out an entire page except one field using Peplecode

Option 1 : Use GRAY() function in the page activate event to gray out individual fields.
Option2: Make page display only. and then in the peoplecode use enable property for the field that needs to be enabled.
OR
Loop through
&Rec= Your Record
for &i =1 to &rec.fieldcount
if &rec.field.name <> 'your req field' then
&rec.field.displayonly =true;
else
&rec.field.displayonly =true;
end-if;
end-fo