Indexed Color won't allow lower than 10 or 13 colors.

[Katy Surface]

Indexed color error: "An integer between 10 and 256 is required. Closest value inserted."

I teach surface design and sometimes my students get this error message when indexing their art down.  We often want art down to less than 10 colors. 

I hadn't recieved it myself until today.  Mine is only allowing me to go down to 13 colors.  I'm trying to get to 3 or 4 on this particular file, but sometimes go as low as 2. 

Any ideas?

-Katy

[melissapiccone]

I used to do this a million years ago when I made video games in the 90's. You should be able to go as low as 2. 

https://helpx.adobe.com/photoshop/using/customizing-indexed-color-tables.html

[melissapiccone]

I was able to do it. I placed only my colors in my image - white background, erased part of it to transparent and used the pencil tool to add the purple. Then I changed it to index color and it took the 3.