It's not a bug per se but the changes to make signs colourable with dye have made the colours lose vibrancy as compared to when in the past altered with the § symbol. The old sign created pre-patch is on the left, and the new sign is on the right for comparison. I've used dark oak as I have stripped spruce behind. When I paint a sign in real life, the colours are a lot more vibrant than the new signs in minecraft
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This issue has already been reported. Duplicate MCPE-117516.
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