This paper describes an exploratory study on the use of reflective markers set during synchronous collaborative learning sessions (reflection in action) for later construction of self-reflection reports upon the collaboration that occurred (reflection on action). During 2 sessions, students used the Visu tool for interaction and marker setting (positive, negative, free) and then report building on the interaction (using markers or not). A quantitative descriptive analysis has been conducted on the markers used and on the reflective categories of the sentences in the reports. Results show that students (1) paid more attention in repairing their relationship than reflecting on learning and task goals; (2) used mainly positive markers to both reflect in and on action; (3) used more their partner's markers in the second reports; (4) reflected more on themselves in the second reports to justify successes and failures, and to express satisfaction.