Why are some conditions greyed out?

Why are some conditions greyed out? - Woman in Gray Tank Top

With the release of Heart of Thorns, I've noticed fighting some bosses that sometimes the condition icons on their hud change from being red to grey.

Here is a poor screen cap from a Youtube video.

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Why do these icons change colour? What significance does this have?






Pictures about "Why are some conditions greyed out?"

Why are some conditions greyed out? - Top view of miniature airplane placed on over gray world map with crop hand of anonymous person indicating direction representing travel concept
Why are some conditions greyed out? - Woman Wearing Gray Long-sleeved Shirt and Black Black Bottoms Outfit Sitting on Gray Wooden Picnic Table Facing Towards Calm Body of Water at Daytime
Why are some conditions greyed out? - Assorted Colored Rocks





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Images: Andrea Piacquadio, Andrea Piacquadio, Oleksandr Pidvalnyi, Ir Solyanaya