Please check my grammar!

''It only looked good'' 的 ''looked''
應該改成 ''looks''

yes i think the grammar is basically correct but the expression 食べ物がいろいろな色で is a bit weird. maybe you can say カラフル or はで which also means colorful.

and please pay attention to the word で
it is used to talk about reasons but not all reasons can be expressed with this word.
で is mostly talking about natural things like earthquake or some phenomenon which are objective and usually cannot control by people. So in this case it's not appropriate to use it in your sentence.

You can use から which is for subjective feelings and the speaker's own thoughts.

i.e. でも、初心者だから料理がおいしく作れません。
食べ物がカラフルだから、料理がおいしそうに見えるだけです。

だis just some gramatical thing added when it's noun or statement before から