I honestly don't know, I don't live in Boston anymore (Manhattan now) but from what I recall, it looked lighter heading to the Fenway area on Storrow so it could just be the angle
I can't remember if there is a thread already but there is a small early rendering for 333 Dorchester Ave https://boston.curbed.com/boston-development/2020/2/21/21147426/333-dorchester-avenue-boston
I don't think anything ever came of it (unfortunately) but it was this. https://archboston.com/community/threads/residential-tower-26-court-st-government-center.5671/
I tweeted them last month about this. To quote "#OneCongress is set to deliver in 2023. Plans are still underway for the second residential tower. Stay tuned for more milestones and updates!"