View Source ExTDLib.Object.StickerFullTypeCustomEmoji (ExTDLib v0.0.4)

The sticker is a custom emoji to be used inside message text and caption. Currently, only Telegram Premium users can use custom emoji.

NameTypeDescription
custom_emoji_idstringIdentifier of the custom emoji.
needs_repaintingboolTrue, if the sticker must be repainted to a text color in messages, the color of the Telegram Premium badge in emoji status, white color on chat photos, or another appropriate color in other places.

More details on telegram's documentation.