This happened to me once and i thought it was pretty cool! I believe it was my spirit guide, the face was smiling at me with such compassion and love, i saw the wonderful colors as well, but right after the first face showed up, another face popped in and it was my mom, smiling at me as if she's saying i'm OK now and i am happy, after she passed away i didn't know how to grieve, i had a hard time dealing with my emotions, so after this experience i felt better... So i'm thinking they are spirits that are close to you? And they could be your angels saying we're here considering you are more sensitive than before... I hope that helps.
If you haven't done so already, I would recommend that the next time this happens you ask the image : "Hi, I'm (insert your name here), what is your name?, who are you?, I would love to know why you are appearing to me, etc." & then go from there.
I would also recommend that you keep a daily journal (either verbal (audio), written or video so that you can record what is going on in your daily life even if you don't think anything important happened that day.
This way you can look at these journals (notes, videos, audios, etc.) over the coming years to compare "then & now", etc.