The wicketkeeper-batsman married Mumbai-based Nikita Vanjara in Mumbai on Wednesday.
Both India and England retained their teams that played the second Test at Trent Bridge.
The jersey is made from Dri-FIT fabric, a Nike patented technology, which reduces cling and enables the skin to breathe better.
Karthik, who could not participate in the camp so far due to his marriage, had batting and fielding practice with other players.
Sehwag, whose very selection for the tour raised eyebrows as he was not even in the list of probables for the series, has probably been left out to accommodate an in-form Yuvraj Singh.
India rung in two changes, Munaf Patel and Dinesh Kaarthick coming in place of VRV Singh and Mahendra Singh Dhoni respectively, for the third Test against South Africa.
"Dhoni is enough. If the other keeper is included, he would just be a passenger," the former India captain added.
'What you are seeing now is the process that we had started. We gave the chance at Indore (against England) to Uthappa and Kaarthick and they are showing their worth now," the former India stumper said.
India were 254 for 3 at stumps on Day 1 in the third Test against South Africa.
Dhoni donned the gloves for a short while during Monday's practice, and the focus was on Dinesh Kaarthick, who kept receiving throws from Greg Chappell and the slip cordon.
South Zone scored a commanding 333 for four against Sri Lanka A on the third day of the Duleep Trophy.
Dinesh Kaarthick and Mahendra Singh Dhoni are nursing ambitions of cementing their places in both forms of the game.
Tamil Nadu set Maharashtra an imposing victory target of 362 runs on the penultimate day of the Ranji Trophy Elite 'B' match.
India Red beat India Green by 39 runs to set up a title clash with India Blue in the Challenger Series.