Red X

[ResearchMonkey]

 

[JJR512]

Yep, that's a red X alright.

 

[Gonz]

Perhaps it'd look better in maroon.

 

[BeardofPants]

Nah, crimson.

 

[ResearchMonkey]

It's an invisible red X

 

[Gonz]

divisible only by itself & 1?

 

[woodman19_99]

that's weird... that's a blue x on my computer