In cryselle 28 the colored pills are the placebo pills and meant for withdrawal bleed to occur, so if you have sex during this period before the withdrawal occurs then the chances of pregnancy would still be minimla as the endometrium would be in the shedding mode .Also, if you have taken the pill religiously and on time everyday without missing any , then pill would have prevented ovulation in this cycle and hence even if you have unprotected intercourse any time of the cycle , an embryo cannot be formed as there is no ovulation. So in either case you are safe , you don't necessarily have to wait for green pills for sexual activity.
I hope i have answered your query in detail,
wishing you good health,
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