The Particle.color field in area effect clouds is read-only

Area Effect Clouds will not use Particle.color even if potion_contents.potion and potion_contents.custom_color are not set.

Previous behavior was to use the color provided by; potion_contents.custom_color, potion_contents.potion, and finally Particle.color

It might still be the same, but Particle.color has become read-only

(One could say it’s probably WAI, and might be a documentation issue, but from what I can tell there is no mention of this in the current snapshot cycle release notes)

Not too sure how to file this, it does seem to be a regression as potionless area effect clouds seems to be intended to be white as default (color:-1), and it will most cause headaches for some datapacks once released.

It’s also oddly jarring to have one property in Particle be protected

/data merge entity @n[type=minecraft:area_effect_cloud] {Particle:{type:block,block_state:"dirt"}}
/data modify entity @n[type=minecraft:area_effect_cloud] Particle.block_state set value stone

is ok, but not for Particle.color if Particle.type is entity_effect 🙂

# 1.21.4

/rotate @s 0 0
/summon area_effect_cloud ~ ~0 ~10 {Tags:[0],Radius:3,Duration:9999}
/summon area_effect_cloud ~ ~1 ~10 {Tags:[1],Radius:3,Duration:9999,potion_contents:{custom_color:-65536}}
/summon area_effect_cloud ~ ~2 ~10 {Tags:[2],Radius:3,Duration:9999,Particle:{color:-65536,type:entity_effect}}
# 0:white, 1:red, 2:red

/execute as @e[type=area_effect_cloud] run data modify entity @s Particle.color set value -16711936
# 0:green, 1:red, 2:green

/execute as @e[type=area_effect_cloud] run data modify entity @s potion_contents.custom_color set value -16776961
# 0:blue, 1:blue, 2:blue

# 25w09b

/rotate @s 0 0
/summon area_effect_cloud ~ ~0 ~10 {Tags:[0],Radius:3,Duration:-1}
/summon area_effect_cloud ~ ~1 ~10 {Tags:[1],Radius:3,Duration:-1,potion_contents:{custom_color:-65536}}
/summon area_effect_cloud ~ ~2 ~10 {Tags:[2],Radius:3,Duration:-1,Particle:{color:-65536,type:entity_effect}}
# 0:black, 1:red, 2:black

/execute as @e[type=area_effect_cloud] run data modify entity @s Particle.color set value -16711936
# 0:black, 1:red, 2:black

/execute as @e[type=area_effect_cloud] run data modify entity @s potion_contents.custom_color set value -16776961
# 0:blue, 1:blue, 2:blue