As stated in my Merry Report comment, I believe he should be in a motely coat. I have a memory of a picture of John Skelton, another Henrican playwright in a long motley coat but I haven't been able to track it down. Did Heywood play the jester too?

Millers sometimes appear mealy faced in plays - i.e. covered with flour and that might be an opportunity for comedy.

I have found an image of Thomas Skelton, the Fool of Muncaster, in a motley coat with a staff, but not one of John Skelton so far.

Costuming Merry Report in motley may well make clearer his liberty to speak on contentious subjects. We did base Merry Report's costume on an image of Will Somers playing the harp in Henry's psalter, with the aim of evoking the jester but in line with the 'naturalistic' costumes of the other characters. It could be that this was rather too obscure however.

Heywood was certainly a royal entertainer and has been construed as a jester, but perhaps more in the tradition of Skelton: a jester-scholar. Beatrice Otto writes that he "used the padding of a jester's folly to soften his strong political views" ('Fools are everywhere: the court jester around the world', University of Chicago Press, 2001, p178).

Do you have titles for the plays in which millers were mealy faced by the way, Peter?

Apologies for my vagaries. The image is likely the one I have seen. I probably confused the names in passing. If it is the image I am thinking of in a long motley coat with a thin staff I think it implies that motley costumes were naturalistic in their way, in that fools both natural and artificial would wear them to denote their status within the household the same way that servants wore livery.

A reference to mealy millers can be found in Wilson’s Three Ladies of London which as the stage direction: “Enter Simplicitie lyke a Miller all mealy with a wande in his hand.” (B3) Not sure what the wand is for but it is curious.

Just to clarify, I have no real conviction that Heywood was a jester as we understand it (I don't know enough about him) nor am I suggesting that Merry Report would be dressed in the Victorian image of a jester with belled hat and bauble. I think a hint of motely connecting the character to the tradition of the fool/jester would support the numerous dramaturgical functions the character serves in the play leading the audience to view him as their compere, master of ceremonies and lord of misrule. Three Ladies contains another useful stage direction:
"Enter Dissimulation, hauing on a farmers long coat, and a cappe, and powle and beard painted motley."
The farmer's coat is a disguise and his beard reveals his true nature. It takes a while for Simplicity to cotton on but eventually he figures Davy is not the "honest man" he took him for saying:
"A bottes on thy motley beard, I knowe thee, thou art Dissimulation" A motely beard Eleanor!

I can't believe I missed the Will Summers reference by the way. That was a great idea, although obscure as you say. In the original context I think the costume would have worked to establish Merry Report as a figure of fun in the same way I am suggesting a hint of motely might work for us today.

It comes down to the position of Merry Report in the play. If he is a spokesperson for the court then would having him in motley work against this? It might place his words in a clear fool / clown context and therefore lessen their impact. At the sametime having MR in motley would work to sustain his status as a licensed fool - and it would certainly make speeches like the 'new moon' speech easier to do.

I believe the evidence in the text that Merry Report is a fool/jester is pretty persuasive especially coupled with the function of the similar central characters in the moral interludes. The production and analysis process of your project appears to be led by the surmised political implications of the text but in this instance I think the internal and contextual evidence of theatrical practice should perhaps be allowed to take precedence. If MR is a court entertainer working in the traditions of folly and misrule what impact does that have on the politics of the piece? Why might Heywood give political arguments to such a character? Does he need the get out clause of the fool's licence? How does the guise of folly change the political argument, or the force and style of that argument? As an outsider to your project, these strike me as exciting questions.

Thanks for this, Peter.  An investigation of how a more clown-y construction of Merry Report affects the text may well be a focus of the second phase of the research. 

Thinking further about Merry Reports costume I think one has to be careful not to make it too obviously clownish, otherwise the Jupiter's decision to appointment him as messenger starts to look rather foolish. If it is impossible for Jupiter to avoid seeing Merry Report as a clown could he make him his representative on earth? In some ways this relates back to the status of Jupiter in the play and whether he represents Henry - or is there a comic slightly carnivalesque side to Jupiter?