The Dongba character for bright, bu˧, is another ideogrammic compound, composed of the characters for sun and moon, both emitting light.
This is if course, almost identical to the Chinese 明, with the sun on the left and the moon on the right, only in the Chinese there is no pictorial representation of the rays of light. Here they are together (Dongba on the left!):
You'll notice the positoning of the 'ideogrammic' elements is also near identical. No one really knows how old the Dongba script is, but it's definitely more recent than the Chinese script, and this seems to be another example of the latter's influence on the former.