The RP would not be used to produce colour so it would not be part of the chemicals inside the flare, ie with the sulphur and colour agent (transition metal salt of some kind usually).
ie-->
http://www.ledlinc.com/safetyproducts/turboflare/data.htm (http://www.ledlinc.com/safetyproducts/turboflare/data.htm)
this is one i found containing strontium nitrate which produces the colour (blue?) and other crap....
are you following a totse method (oh dear....)
http://www.totse.com/en/drugs/speedy_drugs/162384.html (http://www.totse.com/en/drugs/speedy_drugs/162384.html)
talks about road flares... the flares it talks about are still sourcing the RP from a striker on the flare, ie same as matchbooks... so it proves no easier but you would get more RP per flare rather than MB, which is obvious...
But it sounds ok provided you can get the type of flare you still have to bang on the ground (ie use a striker mechanism of some kind) to start it, and provided also you can take it apart without setting it off (oh oh!).
As for your mixture.... oh dear.... well if you tipped the contents of the flare into water and left it... the RP may not even be there... check the body of the flare for some kind of striker pad as with MB's thats where it may be...
What your mix is would possibly be a crystaline aqua complex of whatever transition metal (maybe) or something.... other than that you would have sulphur and misc crap... prob ok to dispose of it.... down the drain should be ok.
-AC