rainbowembed.py

import discord, asyncio
from random import randint
from discord.ext import commands


class RainbowEmbed:
    message = None
    content = None
    def __init__(self, bot):
        self.bot = bot

    async def loop(self):
        while self.message is not None:
            await self.message.edit(content=None, embed=discord.Embed(description=self.content, color=discord.Colour.from_rgb(r=randint(0, 255), g=randint(0, 255), b=randint(0, 255))))
            await asyncio.sleep(1)
        
    @commands.command(aliases=['rbembed', 'rb'], pass_context=True)
    async def rainbowembed(self, ctx, msg_id: int = 0):
        await ctx.message.delete()
        if not self.message:
            async for msg in ctx.message.channel.history().filter(lambda m: m.id == msg_id):
                self.content = msg.content
                self.message = msg
                break
            await self.loop()
        else: self.message = None

def setup(bot):
    bot.add_cog(RainbowEmbed(bot))