The English have an attack speed buff from two possible sources, the Longbowmen Arrow Volley ability and the Network of Castles thing granted by defensive structures to all units in a wide range. Whenever a unit is under one or (only Longbowmen) both effects, it glows yellow.
The Delhi Sultanate too has an attack speed boost from two possible sources, the Tower of Victory’s permanent upgrade to all infantry and infantry archers that come within its radius of effect and the Scholar’s Zeal that improves damaged units attack speed for the duration of the healing. However, other than applicable units entering the Tower of Victory’s radius for the first time, the Sultanate’s attack speed is not visualized by a yellow glow.
Why not? If you didn’t manage to have all your barracks and archery ranges within the tower’s radius, it would be reasonably necessary to see at one glance who slipped through the net and didn’t collect his buff.