WordNet sense 1 (having or emitting a high-pitched and sharp tone or tones ):

piercing, sharp

WordNet sense 2 (used of sounds and voices; high in pitch or frequency):

high

WordNet sense 3 (utter a shrill cry):

pipe, shriek, pipe up

WordNet sense 4 (being sharply insistent on being heard):

strident

WordNet sense 5 (requiring attention or action):

imperative

WordNet sense 6 (having striking color):

colorful, colourful