so, how much air can they handle without out damage

 

None if you are going jumping get red lables

 

If I remember correctly blue labels used to be the only rims you could get in the '80s and people used them for MX and XC racing all the time. The red labels are stronger but since you are riding a 250ex I don't think you'll be able to get enough air to hurt the blue labels before exceeding the limits of your machine. Might as well save some money and go for the blue labels.