What is a Base?

 pH means potential/power of Hydrogen

The strength of an Acid is measured on the pH scale, it starts from 0, to 14.
If the water turns-

-Red it is 0-1 on the pH scale
-Orange it is 2-3 on the pH scale
-Yellow it is 4-6 on the pH scale
-Green it is 7 on the pH scale
-Blue it is 8-9 on the pH scale
-Indigo it is 10-11 on the pH scale
-Violet it is 13-14 on the pH scale

As you can tell it is all the colours of the rainbow
Adding a few drops of Acid makes it from 0-6 depending on how much you add 
Adding a couple drops of Base makes it go between 8-14 depending on how much you add
having it balanced in the middle makes it green, the number 7, on the pH scale, also meaning its just plain water, 

How it works is the acid and the base balance each other out, meaning they both are basically not even in the water.

Also to make it work put green food colour into the water making it plain green water, also when you add the acid or base, stir it, but don't use something that can change the outcome, r that the acid or base will harm.

pH is the log, or the hydrogen concentration, log is a mathematical term for counting how many decimals there are in a number.

Any Base is the polar opposite chemical of any Acid.

A Base contains hydroxide as an Acid contains Hydrogen.

adding the same amount of Acid and Base makes them cancel each other out, where as if there is more acid, the acid will take over, and vice versa.

H (Acid) -OH (Base)

An Acid and a Base neutralises the chemicals creating HOH or Water (H2O) 

Conclusion

A base can be different things in chemistry, more known as a chemical, that changes most things colour, like it can change plain green water, to a cyan, deep blue, indigo, or violet, and can change red litmus paper to blue, It's also known as an polar opposite of the other chemical, Acid.