it would be great to diversify the gray combo colors (now we have the same tone) by adding a bit of contrast
excessively monochromatic colors can make it harder to perceive combo patterns, thereby reducing the map’s readability
the lyrics of the song reflect the inner struggle, the feeling loneliness, the desire for self-awareness and the desire to fill the world with colour again
through the images of grey, blue and blue, the path from emotional isolation to the awakening of feelings and hope is conveyed. the play of colours can be beautifully played on this
u don't necessarily have to use shades of blue, u can generally do collorfull, either way it emphasises the point of the song
it sounds fine, also these hitsounds are ranked here https://osu.ppy.sh/beatmapsets/1972407 (my and shime's diff)