Brown mustard color on my Mammillaria cactus

[Stratt]

I would like to post a picture of my cactus which shows the color of the damage but I get an error message that it is too large. The photo is on my I phone camera. Would this color be sunburn?

[MagiCarpus]

The best way for us to help you with your plant is if you'd still upload a picture.

Here are the detailed instruction on how you can do that:
viewtopic.php?f=2&t=25028

The way I upload mine was through Imgur. Once you got the picture on imgur. Select "get download link" >> "BBcode"