1F308 (rainbow)

symbolically tolerance of diversity

(are those supposed to be clouds below, or land?)

the artist's palette emoji also suggests a range/choice of colors

folklore imagines a pot of gold
Judy Garland imagined heaven/utopia

real rainbows always have the red on the outside (and the sky is usually much darker outside the rainbow than inside it)

1F307 (sunset over buildings)

equally sunrise

1F306 (cityscape at dusk)

equally at dawn
no visible sun

1F305 (sunrise)

mostly over water
equally sunset

1F304 (sunrise over mountains)

is it just Japan that assumes mountains (or sea?) are in the east and cities are in the west??

in any case, the sunsets can't be reliably distinguished globally, although some have a slightly darker sky

1F303 (night with stars)

dark-sky versions make the cityscape very hard to see, light-sky versions are confusing so a crescent moon is added

cf cityscape at dusk
foggy (may have cityscape)
sunset over buildings
bridge at night
milky way

sunrise over mountains
sunrise
Mount Fuji
volcano

office building

the earliest Docomo emoji set included 'Night'

1F301 (foggy)

modifier: maybe
uncertainty
approximately