Sweet Emma I, too, have always wondered what the different colors in our dreams mean so after reading your post I spent some time looking it up for you, myself and others who may be interested and here's what I came up with for the colors
yellow and
blue since you said that Elvis was wearing a
light blue jumpsuit in your dream:
Yellow
Yellow is symbolic of the intellect in dreams. It reflects the use of mental faculties and if someone who approaches the dreamer wears yellow in the dream, it may indicate a need to challenge one’s intellect or to spend time engaging in rational thought.
Blue
Blue can mean many things in dreams, depending on the shade. In general blue is a representation of the dreamer’s moods. Dark blues may be foreboding, or an indication of worry or fear. Lighter blues may symbolize hope, healing and a high level of spiritual awareness
Now as for what the color
yellow has to do with Elvis, I unfortunately do not know how to interpret dreams as well as some of the others here, but it says here that the color
yellow is symbolic of intellect and we all know what a smart and wise man Elvis was.

Now as for the
light blue suit that he appeared in, according to what it says here, maybe he was trying to give you hope for things that may be going on in your life, or perhaps trying to help with healing in that regard, or help to somehow increase your spiritual awareness?

I think that
blue was one of his favorite colors too so maybe that could possibly be why you saw him wearing that particular color suit?

As I said, I am not all that good at dream interpretations, but just trying to give you my best guess based the information I found about these 2 particular colors.

One thing I can tell you for certain is how incredibly handsome and good looking he was wearing
BOTH of those colors!!
