Choose three terms of brightness and analyze the meaning and effect of these in Romeo and Juliet?
William Shakespeare's tragedy of Romeo and Juliet is replete with light/dark imagery, and the second act that contains Romeo's beautifully poetic soliloquy as she sees his new love appear is memorable for its figurative language:
But, soft! What light through yonder window breaks?
It is the east, and Juliet is the sun!
Arise, fair sun, and kill the envious moon
Who is already sick and pale with grief
That thou her maid art far more fair than she (II,ii,1-6)
The first line contains a metaphor in which Juliet is the light; she is also compared to the sun in a metaphor. The third line contains apostrophe as Romeo addresses the sun, telling her to "kill the envious moon," using personification as the moon is given the human quality of envy. Romeo does not wish the moon actually to be killed; he simply wants to revel in the sole vision of his beautiful Juliet.
In a previous act, Romeo is equally taken by Juliet's startling beauty. For, when he first sees her at her party he remarks,
Oh, she doth teach the torches to burn bright!
It seems she hangs upon the cheek of night
Like a rich jewel in an Ethiop's ear--
Beauty too rich for use, for earth too dear!
Again, light/dark imagery is employed as the torches are taught by Juliet to burn brightly against the night. Personification enters with the "cheek of night," as well as the dark imagery. A simile occurs in the line in which Juliet is compared to a rich jewel in the ear of an Ethiopian ear. This simile also contains light/dark imagery.
The effect of this light/dark imagery and exaggerated use of metaphor and apostrophe is parallel to the spontaneity with which Romeo falls in love. Like Friar Laurence's warning,
These violent delights have violent ends
And in their triumph die, like fire and powder
Which as they kiss consume. (II,vi,8-10)
the light/dark imagery suggests the dangerous and explosive quality of Romeo's feelings.
Please rephrase your question so we know what three things you are talking about.