The yellow rear sight fiber-optic on these TFO sights is intentionally designed to be dimmer than the green front sight. This allows for greater front sight visibility and acquisition…a preference for many shooters.
Please see the detail from the TFO (yellow) rear description from our website:
https://truglo.master-7rqtwti-evtrxkbyim2ii.us-3.magentosite.cloud/tfor