rtv comes in several colours including blue. I have seen orange, red, blue, black, clear and copper. RTV stands for room temperature vulcanizing which basically means it cures at room temp. there are different uses for the different colours of the automotive brands of rtv. the right stuff is also rtv silicone but it has been formulated to cure fast, so it is thicker and a little harder to work with because you gotta be quick with assembly. there are also other handiman brands, or types, of rtv which come in all sorts of colours but a lot of those are not oil resistant. some of the automotive rtv is also not oil resistant. it is always good to know the rtv you have so you dont use it improperly.
here is a little write up on the permatex brand and their colours and uses
https://4lowmagazine.com/rtv-colors-...20applications.
and here is one from the jbweld site with their colours
https://knowhow.napaonline.com/jb-we...ilicone-guide/