Changing Body Background Color with Retention Theme (light)

Sorry in advance if this is kind of a stupid question, but I am REALLY new to this!

I have tried changing the body background color on my site with some codes on I found in other forums. Unfortunately, when I change them it doesn’t change anything on my site.

(www.clfmusictherapy.com) – I’m trying to get the body background color to be color 363636 (the grey color in the header)

I am also trying to figure out what the other color is at the top of the page in the header (blue, teal, or something like that). I can’t seem to match it & would like my text to be that color.

Any help at all would be greatly appreciated!