The short answer is "not just using merge fields".
Some circumstances in which you might be able to do it just using fields:
- If you apply bold to the word "blue" (i.e. the third word), then add the *Mergeformat switch to the MERGEFIELD field, Word should apply the bold formatting to the third word in each value it merges using that mergefield. However, if any of the values merged have fewer than 3 words, Word may revert to not bolding the third word. And then there's the question as to what Word considers to be a "word".
- If you are merging from a document data source (e.g. a Word document, an RTF document) then you may still be able to use
{ thefieldname }
instead of
{ MERGEFIELD thefieldname }
but this is "legacy behaviour" that dates back to the time when there was no MERGEFIELD field type, and
a. I don't know whether it works in recent versions of Windows Word, or Mac Word at all
b. I suspect only some formatting features "get through"
Other ways to do this are to postprocess the merged text or use MailMerge events to modify the MERGEFIELD result formatting.