How to make home made fresh ginger garlic paste with out changing color

Ingredients
1.Ginger root (wash ,peel and chop) - 1cup
2.Garlic - 1cup
3.Oil - 1/4 cup
4.water - 1/2 cup

Method:
Blend all the ingredients together into a fine paste.Store into air tight container.It will last more than a month with out changing any color.