Assuming that the instrument’s parameters are appropriately set for the range of velocities to be depicted in color when superimposed upon the gray-scale image, RED means flow in one direction while BLUE means flow in the opposite direction. A mixture of RED & BLUE together can be the result of circular flow, turbulence, aliasing, or insufficiently resolved coherent flow.
Power Doppler is a form that is more sensitive to slow flow, but is depicted as one color, e.g. gold, orange, yellow to indicate only its presence but no information as to which direction it is, if any.
The bubble that you see is probably the amniotic sac that contains the amniotic fluid into it, and the tiny thing u see inside was the baby. Measurements of the baby are also taken the time you go in to have an ultrasound, this is to see how well the baby is growing inside.
There are other forms of Ultrasound Imaging which employ color to connote, for instance, the use of harmonics. Such color assignments are proprietary, i.e. depend on the manufacturer.
There are strict rules laid by the government and the health ministry about what ultrasound technicians are permitted to tell patients and what not to tell. Like in some countries the sex of the baby isn’t disclosed till the time of delivery. The technicians are just there to take a good record of the baby the rest is upon the doctors to tell, So you need to talk to your doctor to see how things are going inside your belly. Your doctor will go through the reports thoroughly.