Why did van gogh feel it is not enough to paint white spots on a blue black background?

II found this quote. I think it answers your question. I think he was saying the white dots weren't enough detail. with how beautiful a starry sky looks, he wanted more color in the picture and wanted it to show detail and emotion.

“At present I absolutely want to paint a starry sky. It often seems to me that night is still more richly coloured than the day; having hues of the most intense violets, blues and greens. If only you pay attention to it you will see that certain stars are lemon-yellow, others pink or a green, blue and forget-me-not brilliance. And without my expatiating on this theme it is obvious that putting little white dots on the blue-black is not enough to paint a starry sky.”

everybody they have a little secret something

that they don't wanna tell anybody

because it's shakin'

yeah yeah

like when your hearts racing

from having stage-fright

listen up

say okay i-i understand you but

you don't ever have to hide

no no

just look it in the eye

don't be afraid of letting go!

if you don't try you'll never know

and whoa whoa

if you really wanna win

you gotta dive in

come on now you know it's time

you never know what you may find

and whoa whoa

if you really wanna win

you gotta dive in

yeah yeah yeah yeah

hey!

time to stand up

don't have pretend

and if you mess up

just go and try again

no don't worry

you're surrounded by your friends

yeah yeah yeah yeah

don't have to hide out

don't need to fear the worst

nothing's scary

as they seem at first

hey you're a monster

you can do it that's for sure

come on come on

don't be afraid of letting go!

if you don't try you'll never know

and whoa whoa

if you really wanna win win win win

you gotta dive in

come on now you know it's time

you never know what you may find

and whoa whoa

if you really wanna win

you gotta dive in

yeah yeah yeah

you gotta face your fears

yeah yeah yeah

and they will disappear

yeah yeah yeah

what are you waiting for

yeah yeah yeah

come on

don't be afraid of letting go

if you don't try you'll never know

and whoa whoa

if you really wanna win

you gotta dive in

come on now you know it's time

you never know what you may find

and whoa whoa

if you really wanna win

you gotta dive in

c. landscape orientation