Steps:
- Find and save/copy an example image of the color you want
- Paste image into discord
- Type /prefer option set to option the menu to set a custom option
- Click one more and select value
- Drag the color that you pasted into discord into the value field
- In option, you name your color variable e.g. orange
- To reference our color variable, type in your prompt and then write –cref for character reference and then — and the name of your color variable e.g. an ocean wave –cref –orange
a batmobile –cref –orange (using hex colour #fb2e00 as the orange value):

But MJ struggles with this concept when you ask it to add unnatural colours, for example, an orange ocean:

By tweaking the prompt a bit, I got there in the end:

How about combining saved colors? Just type –cref –firstcolor, –secondcolor i.e. put a comma between your first and second colors.
Example: an orange man wearing purple clothes –cref –orange, –lav
Pretty good!

If you’d prefer to watch a video, this tutorial was based on this video by FutureTechPilot:
