Hikari in Chinese / Japanese...

暉 is a Kanji that often represents a Japanese name romanized as Hikari.

The literal meaning can be sunshine, light, or to shine upon. It has the same meaning in Chinese and Korean. From ancient Chinese, it is a variant of 輝/辉.

Other Japanese romanizations include Hikaru, Hikatsu, Teru, Terasu, Ki, and Akira.

光彩 is the Chinese, Japanese Kanji, and old Korean Hanja for radiance.

Other meanings include luster, splendor/splendour, and brilliance.

光彩 is the radiance you see when a person's arrival brings happiness and joy to the room. Or the radiance on the face of a new bride etc.

If you delve into the dictionary, other forms of radiance will refer to isotopes emitting radiation. 光彩 is not related to radiation and is not the kind that causes cancer.

In Japanese, this can be several female given names such as Misa, Hikari, Hiiro, Teresa, or Arisa. And a more unisex given name of Kousai or Kosai.

光 is the simplest way to express “light” in Chinese, Japanese Kanji, and old Korean Hanja.

It can also mean ray or bright. Chinese tend to use a two-character word for light/bright, so this character is probably best if your audience is Japanese. Also, when pronounced Rei, this can be a Japanese female given name.

In the Zen Buddhist context, this is the pure light that everyone possesses at their origin.