Your question is how to get colour correct.
I will assume from this that you mean white balance, which is how to get colours to appear "correct", as in not coloured or tinted and without colour cast which are caused by the ambient light.
If this is the case, some basics:
Always shoot in RAW; this allows complete control over white balance when processing the RAW image.
Set a white balance reference for the ambient light; place a neutral gray card in any shot where you will be taking a number of pics, and where the light wont change; if light changes, you will need to set a calibration point for the new light conditions. Then, when performing RAW processing, use this gray card to tell you RAW processor to use this as a WB reference, and apply the resulting WB settings to all shots taken in this light.
This is easily done in set or posed shots (you only need the card in one test shot!), not so easy here with a candid, however you can still use what you know to be white as a reference in RAW processing.
ALWAYS use a flash to provide fill in light. You will see all Pro togs doing this is you watch. It will fill in shadows, provide catch lights in eyes, and is a safety net in a manner of speaking to ensure you get more good shots that not so good.
Now for this shot:
Its underexposed, and unevenly lit from left to right - fill in flash would work well here!
There appears to be a mix of light types, so not an easy job for auto white balance, - and again, shooting in RAW will let you make the best of the situation. On my screen there is an overly yellow tone (incandescent lights perhaps?) that RAW WB would compensate for, - and in my mod Ive used colour balance to try to get it right. To do this, I made an assumption that the brides dress is close to white, and adjusted colour balance to get it as neutral as possible (this means R G and B are close to the same values)
I have cropped space from the left, and added a little height, while compensating for the uneven lighting , - lifting the light on the grooms face.
I hope this gives you something to work on and answers your question. If Ive missed the mark, let me know.