This is the 4865th most frequent Japanese word.
無難
"Safe; acceptable; free from fault or risk."
無難な (bunan na) is used to describe the color as 'safe,' implying it won't attract unwanted attention or create a clash in any social context.
この服は無難な色なので、どんな場面でも着られます。
This clothing has a safe color, so it can be worn in any situation.
無難な (bunan na) here qualifies the way of answering as 'safe,' meaning it avoided controversy or conflict.
彼の無難な答え方が、会話をスムーズにしました。
His safe way of answering made the conversation smooth.
無難に (bunan ni) means 'safely' or 'without trouble' in this case, indicating that the exam was completed without any major difficulty.