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Nounにする and Nounになる

～にする and ～になる are similar to each other, but differ with regards to the actor:

にする implies a decision or effort by an actor.
になる implies a natural change or result. (no actor)
This particular meaning must be used with nouns.

Caution:
You must use に and not を。

あかをなる✖ – I become to red. Literally you are doing “become” to red.
あかをする✖ – I do red. “red”ing.

Nounにする

To decide on
Noun + にする (to decide on)

～にする is a pattern that means to “decide on”. It can only be used with used (in this sense) with nouns. it indicates a decision.

Examples

あかにした – I chose red./I decided on red
パスタにする – I choose pasta./I decided on the pasta. (at a restaurant)
ご飯にした – I chose rice./I decided on rice.
ピカチュウにした – I chose Pikachu. (as my starter)

Nounになる

To become
Noun + になる

～になるis a pattern that means to become. It indicates a a change in state.
The actor for なる is the thing itself. It cannot be done by a third party. (Intransitive)

Examples

あかになった– It became red. (on its own)
パスタになる – It will become pasta. (naturally if cooked)
彼がサイボーグになった – He became a cyborg. *
*Although someone probably made him into a cyborg, there’s no actor in this sentence.

See also: ことになる and Adverb＋する・なる