“Correct" and “right" usually means "对” or “正确” in Chinese. （对dui4/ 正确 zheng4que4）However，“对” and “正确” is not quite good when we translate these two sentences. Personally, I think these sentences can be translated into Chinese like that: 1.这件衬衫的尺寸很适合你。（shi4he2） 2.那是你应该用的笔。 Hope my answer would be helpful for you. : )

Absolutely.

Is there a difference in the answer? I am unaware of differences in those contexts that you describe.

“Correct” means “正确的”（zhèng què de）,and “right” also has this meaning. About the two sentences: 1.This shirt is the correct size for you.Translation of this sentence is “这件衣服的尺寸很适合你”.(zhè jiàn yī fú de chǐ cùn hěn shì hé nǐ) 2.That is the right pen you are using.Meaning of this sentence is "这就是适合你用的那支笔".(zhè jiù shì shì hé nǐ de nà zhī bǐ) This sentence translation is literal translation,because I know the meaning of this sentence, but I don't know how to express it .I'm so sorry.

I'd like to point out that both "correct" and "right" have different meanings when used as a verb than when used as an adjective. Also, both your examples have a conversational context and the translation would thus be an informal phrasing and not the straightforward "对的,正确的" that you would expect.