I have a question regarding mint plant. As you can see attached image, in which mint leaves are having very light color. Normally, mint leaves are in dark green. Is there any deficiency?
All the above are possible and difficult to diagnose.
However, you need to consider the plant:
Mint is a Mediterranean plant and needs very little organic matter, poor soil and very little water. It creeps around in open soil to find these things to survive.
There could be too much of all the above but I would say over watering is the case here. If the plant takes in too much water, the stomata in the leaves close to reduce the water in take from the atmosphere and reduces photosynthesis, eventually killing the plant which is not able to manufacture food for itself. How often do you water and how?
Yes, you are right, your mint has a deficiency. A chemical deficiency, not nutrient 'causes plants have to have just the right chemistry so they can make their own food via photosynthesis. Have you ever given it any fertilizer at all? What kind of soil? Hopefully you've used sterilized potting soil, all you need is a simple balanced fertilizer. The best for safety and those not into testing...is Osmocote 14-14-14, use half the amount and half the applications. Major difference. Apply once maybe twice a year. That is it. Extended release.
This looks like it could be magnesium deficiency. Magnesium deficiency can result in yellowing leaves with green veins.
You could give the plant some epsom salt, which is magnesium sulfate. Or another kind of magnesium should work.
Excessive heat can result in magnesium being unavailable. Supplementing with excess magnesium in the soil probably won't help in that case (but a foliar spray might).