We suggest taking a little baggie with you, into which you can place a wet bedikah cloth when necessary. An envelope would also be fine, but a baggie is less likely to get stuck or to take off some of the discharge from the cloth. When you get home, you can let the bedikah cloth dry before bringing it for evaluation.
If you forget to bring a baggie and don't have any suitable receptacle, it would be permissible to omit a bedikah in these circumstances. Be careful to perform your other bedikot, and remember that you must perform at least one bedikah on day 1 and day 7 of the clean days.
If you find the same colors repeating themselves, you can ask your rabbi if you can assess any of them by yourself.
Please write back with any further questions.