It’s not uncommon to have a little bruising after a blood draw. Occasionally. if there isn’t enough pressure applied or the bandage is removed too soon after the collection, the blood can continue to leak out from the vein and collect under the skin causing a much larger bruise.
It can take time for the body to break down the blood and fluids that accumulated in that area. As that happens the bruise turns different colors.
Within the first few days after getting a bruise, the area may become black, blue or purplish. About 5 to 10 days after getting a bruise, the area may turn greenish or yellowish.
During the final phase of healing, approximately 10 to 14 days after getting a bruise, the area will usually be brown in color. Eventually it just fades away.
I’ve had some experiences with blood draws and had a couple that look very similar to yours, so I’d hazard a guess that there wasn’t enough pressure applied under the bandage after the blood draw.
In your photo I can see it’s already turning greenish/yellow which fits the time frame for labs. The dots will take a little longer to completely fade but it looks like it’s following a natural progression for resorption of the blood in a bruise.

The next time you have a blood draw just let the phlebotomist know what you experience and ask for a pressure bandage. Instead of a bandaid with a little gauze tucked under, it will be more of a band of athletic wrap with a larger piece of gauze to put more pressure on the needle poke site. Just keep it on for 30 minutes and it should be fine. ☺️