Can i connect - to + connectors???

Yes you can, the LEDs have this annoying habit of not working in one direction and working only in the other(Since they are Diodes), but since most manufacturers of Cases and Mobo's vary when it comes to naming the + & - terminals correctly it's always very confusing when you match the + to + and the lights still don't come on.
Well, as long as they only the LED terminals or the Power and Reset switches, I don't see any harm from reversing the polarity.
It can and usually works.....
 
It really doesn't make that much of a difference, the HDD LED contact pins on the Mobo should have a small print on the Mobo beneath the pins saying + & -. Usually the White wire is the - and the colored wire is the +. So in case you have the Mobo manual you can find the exact pins on the Mobo to put them onto.