What speaker cables are which ? Please help

[Fpnyme]

    Hey guys I have a 17 plate Citroen berlingo with the multimedia head unit . I have recently installed a underseat sub & im not 100% I’ve connected the speakers correctly . I managed to identify the speaker cables ... well what’s right & left anyway but I’m not sure what’s positive & what’s negative . 
Today I noticed my left speaker sounds really good and bassy but my right speaker is sufficiently quieter and less bassy almost kind of fuzzy . I’m not sure if this is because I have connected the + - to the rca of the sub incorrectly or if I have wired up the speakers wrong (I also upgraded my speakers). Please could someone help me i have looked for wiring diagrams online for hours but can’t find anything. Thank you 

I managed to figure out the speaker cables are the pink , white , yellow & red