The 20-year-old defender is happy with the terms he has been offered and is expected to a sign a six-year deal, as the Blues finalise the remaining details before it is made official.
Mauricio Pochettino has played a role after face-to-face talks reassured Colwill amid concerns the centre-back had about a lack of involvement in the upcoming season.
Brighton had been refusing to give up on the centre-back, with the Seagulls having two bids rising to £40million rejected as Chelsea insisted the homegrown star is not for sale.
Brighton have also tried to leverage Chelsea’s interest in midfielder Moises Caicedo to secure Colwill.
They have, however, failed to convince the Blues. In turn, Chelsea now face paying the full £100m asking price for Caicedo, who is the Chelsea’s first-choice target to strengthen in midfield.
Chelsea also want Brighton goalkeeper Robert Sanchez provide competition for Kepa Arrizabalaga. Sanchez has just two years left on his contract but has fallen out of favour under Roberto De Zerbi.
The Blues are set to announce Monaco defender Axel Disasi and Rennes midfielder Lesley Ugochukwu as new signings in the coming days.