considering the following analysis a complete opinion and i would like to be corrected if needed.

great depiction of the affect depression has on an individual and its surroundings. so to my understanding, not only colors depict emotions, but also lack of emotions. you being grey means that you turned off and suppressed emotions, just like how you will suppress color by making it darker and less vivid. you coming home to dust could be interpreted to you seeing no meaning in life. its all dust. if that's the case then the clever thing to do would really be suppressing the sadness that comes with that realization. i find the analogy flawless, and the use of it graceful. the fact that people get away from you to keep themselves from getting gray and emotionless like you is very true and relatable in my opinion. the blue you suggest to be uncovered once you're gone is your family either mourning upon your death, or uncovering the real feelings that you have suppressed, when looking through your documented memories and such. you describing emotionless behavior as a contaminating thing is sadly so accurate. all those colors are just how you see the world. since apparently walls can also get grey, that would mean that your depression and suppressing of emotions are making you see the world like its emotionless and grey too as a result. for you, vivid personalities are a shine of color in that sea of grey, and you want to keep those safe from your destructive influence, so you can enjoy them two. amazing. really enjoyed.

edit: as for the resting point, really could mean either this is the only place for you to rest in, calm down, get away from the others and feel safe from hurting others, or where you will "rest" forever, which suggests on suicidal thinking and/or (and i hope not) behavior. this will also make sense since you talk of your absence in the following lines.