If a ship's HP ratio is between '''0.665365 and 2/3''' (for example 233/350 on the [[Aircraft Carrier Princess]]), its battle banner's HP bar becomes black.
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*This is caused by some rounding error in the calculation of the green-ness of the color. Within this range, the green color would become round(>=255.5) = 256, causing an overflow in the final color value, resulting in the color 0x1000000 being used instead of a color around 0xFFFF00.
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*It is possible to find at which HP value(s) this happens given a max HP using this [https://flatisjustice.moe/bugs Calculator].