How to default post and page images without image border

I've noticed when I insert an image in a post or a page, it has a default image border and I am having to manually eliminate the border ... because I looked, but was unable to determine where in the CSS to change this default -- I don't want to change the entire theme default, just the images I am inserting into new Pages and Blog Posts. Could you tell me if possible how to do that? Thanks!

**UPDATE ** Please disregard... just realized the appearance of the border is happening in the WP Editor when I am creating the post/page content - the border is displaying on my inserted images, but in the actual live post, it is not showing.

Thanks!