Flags of Protection

The Red Cross (and Crescent and Star of David I assume) is recognised under international law as a symbol of protection, and has in general been recognised as such by combatants. (Yes, I'm sure we can all think of examples where it hasn't, but in general it is.)

The red cross on a white field is a symbol protected under international law, and in theory any use of it except as a symbol of medical/hospital facilities, is illegal. I think many countries have enacted this into their domestic law.

Similarly I believe the UN flag has been used to mark areas or places under UN protection. I think it's only fair to say that its record is rather less successful.
Roy Stilling 07 March

Protection of Artistic and Scientific Institutions and Historic Monuments

15 April 1935

1The High Contracting Parties, animated by the purpose of giving conventional form to the postulates of the Resolution approved on December 16, 1933, by all the States represented at the Seventh International Conference of American States, held at Montevideo, which recommended to "the Governments of America which have not yet done so that they sign the 'Roerich Pact', initiated by the Roerich Museum in the United States, and which has as its object, the universal adoption of a flag, already designed and generally known, in order thereby to preserve in any time of danger all nationally and privately owned immovable monuments which form the cultural treasure of peoples", have resolved to conclude a treaty with that end in view, and to the effect that the treasures of culture be respected and protected in time of war and in peace, have agreed upon the following articles:

...

ARTICLE III

In order to identify the monuments and institutions mentioned in article I, use may be made of a distinctive flag (red circle with a triple red sphere in the circle on a white background) in accordance with the model attached to this treaty.

...

signed by the US and other Pan-American Union states.

I don't know how extensively has the pact flag been used.
Will Linden, 12 March 1996

See also:

• International Banner of Peace (Roerich Movement flag)

The white cloth is, actually, and if I understood it well, not a sign of surrender, but a sign of truce or ceasefire, and request for negotiation. However, since it is more or less that the weaker side is requesting ceasefire in any conflict, and since the result of such negotiations would in most cases result in surrender of the weaker side with more or less conditions, it is easily "extrapolated" as the surrender flag.

In times when things like war ethics were obeyed (was there ever such times?), I guess, it was usual that the "ambassador" of the other side carrying the white flag contact the other side for the "final" negotiations before the fight, to find possible ways of avoiding the battle. At least that is what we are told in many books and movies, but how much this holds, I do not know.

In any case, the white flag is nowadays often seen used by refugees and civilians caught in the middle of battles. It is not unusual to see on TV reports a group of civilians carrying a white flag trying to get out from between two sides. The message sent with such white flag say something like this: "Here we are, we are unarmed and not engaged in you conflict, we just want to get out of here. By carrying this flag we are aware that you can shoot us easily, but we really on your mercy."
Željko Heimer, 6 March 2000

White Flag in England

'Abroad they hold forth a white flag of accommodation and satisfaction, and of minding the same thing which ye mind, and to be flesh of your flesh and bone of your bone, and to invite you to their headquarters, ...' - This is from a Leveller pamphlet which was attacking Cromwell, Ireton and other members of the General Council of the Army, probably written by John Wildman a soldier in the New Model Army, in 1647 (reference source quoted: Woodhouse, Puritanism and Liberty, p. 440).
David B. Lawrence, 16 July 2008

Green Flag in Britain

I had read a novel that depicted a green flag marking a rallying point for Quakers after the Fire of London and I sent an email to the author asking if she had an actual source for this detail, but she did not reply. I still do not have a source for an actual flag, but I've just read In A Free Republic by Alison Plowden, which mentions on p. 49 the House of Commons besieged for three days by five hundred of the 'bonny Besses in the sea-green dresses', who were 'lusty lasses of the Levelling party' - 'green being the colour associated with the Levellers'. 'Eventually, on 25 April, twenty ladies of the 'sea-green order' were admitted to the Lobby with their petition' which was for the release of the Leveller leaders taken prisoner, who later came to trial in September 1649 and were acquitted. (Her reference source is: P. Gregg, Free-Born John: A Biography of John Lilburne, pp. 271-2, London, Phoenix Press,2000).
David B. Lawrence, 16 July 2008