They wrote the notice in big red letters so that it would stick out.

他们用红色大字写出通知，这样会显眼一些。

《牛津词典》

Under the ship, he printed in big red letters: C-O-N-G-R-A-T-U-L-A-T-I-O-N-S!

在船下面，他用红色大字写着：C-O-N-G-R-A-T-U-L-A-T-I-O-N-S！

youdao

We often denote danger by red letters.

我们常常用红字表示危险。

youdao

She used the time in a hospital to write letters in support of an American Red Cross organization.

VOA: special.2009.07.26

This, in clear red letters, is what happens when economics go wrong.

BBC: Greece: What's burning is consent

The day I visited the prison-turned-museum, a woman was outside it selling T-shirts, one printed with "Good Morning Vietnam" in red letters.

CNN: 'Hanoi Hilton' now holds only painful memories

Experts say shoppers should prepare themselves for a high street where the dominant colour is red: as in posters with big red letters advertising year-round sales and many more "For Lease" signs.

BBC: 99p store