The bug

A potion with a potion effect that has ShowParticles set to 0b uses always the same color no matter what potion effect is used.

How to reproduce

1. Use the following command to give yourself a potion with ShowParticles:1b

   /give @p potion{CustomPotionEffects:[{Id:1b,ShowParticles:1b}],Potion:"minecraft:water"}
   

2. Use the following command to give yourself a potion with ShowParticles:0b

   /give @p potion{CustomPotionEffects:[{Id:1b,ShowParticles:0b}],Potion:"minecraft:water"}
   

The reason

The following is based on decompiled version of Minecraft 1.9 using MCP 9.24 beta. All method and class names are the names used in the decompiled version.

The reason why this happens is that the method net.minecraft.potion.PotionUtils.func_185181_a(Collection<PotionEffect>) only calculates the color if the effect shows particles. This is done that way because the value 0 is used to indicate that no particles should be created. A third value should probably be added to indicate whether particle effects should be displayed or not. Another way to solve this could be to have one byte value instead of a boolean for whether or not the particles are ambient which stores a value representing the state, for example:

Affected methods

• net.minecraft.entity.EntityLivingBase.updatePotionEffects()
• net.minecraft.client.renderer.entity.RenderTippedArrow.getEntityTexture(EntityTippedArrow)