My thinking goes along these lines:
Blue is a receptive colour. A rose is a feminine symbol, and a symbol of feminine beauty. It convinces just by being there. Swords are aggressive and cutting. Together, we have the blue rose bringing peace and balance between two crossed swords - duelling swords, suspended by the gentleness of the rose. This gives everyone a chance to stop fighting and reach an amicable resolution of conflict. The blue rose is the mediator.
This fits the Moon in Libra - that is a feminine planet, reflective, but influential in a very subtle way on everything watery (tides, female periods, moods...); and a sign whose ruler is Venus (like the Empress), and whose vocation is to harmonize and bring balance.
To me, the blue rose is a kind of Jimmy Carter in this card.
If you start with the suit at 10, you get the pain - war, feud, domestic strife, mental breakdown, etc. You work your way towards the Ace, step by step, going through all sorts of pain and horror (9 of Swords), a locked position without possible resolution (8), a false truce because of compromise -giving the opportunity to rearm for more fighting (7), a time of detachment and tactics (6), a defeat, but not the end of the war (5), a truce (4), a realisation there is no winning this one, by either side, and that too much has been lost and damaged - and the consequent sorrow (3), a realisation that the only way through is real negotiated peace, based on justice and equality (2), and finally - a resolution: truth and light triumph (Ace).
The blue rose in that progression comes just after the torn rose of the 3 of Swords - a promise of new life after the damage of war: if we agree to lay down our weapons and talk.