Translucent teeth can be a sign that there is something wrong with your teeth. It is mostly related to thinning of enamel (outer most layer of the tooth), leaving your teeth more vulnerable to damage and caries.
Yes, it is safe to swim while you on periods. Period blood doesn't flow outside the vagina like it usually does due to the counter-pressure of the water. But You still need to wear some a tampon or a menstrual cup to avoid getting into a sticky situation.
Resin tooth filling typically contains a filler particle such as quartz, which provides the mixture's strength and color. It is costly as compared to silver tooth filling.
In some cases, the change in period blood color can indicate a health problem like fibroids, low estrogen levels, and even vaginosis.