A really obvious bright red stain in the middle of a white couch is an example of something that would be described as noticeable.
- readily noticed; conspicuous
- worth noticing; significant
- Evident; observable: noticeable changes in temperature.
- Worthy of notice; significant: a noticeable change in the composer's style.
(comparative more noticeable, superlative most noticeable)
From notice +"Ž -able.