I was R031 and still a CV3. I was born this way and nothing can be done to change it.
The colour vision rating is more of a safety thing for yourself and the troops around you.
Colour codes on arty rounds, gernades etc for quick visual ID. No one wants to fire the wrong round on target or wrong colour smoke etc.
There are trades that are closed to you when you are CV 3 but does not mean the end of a career in the army. Have the recruiting staff go over your vision rating and see what trades are still open to you.
The book test is not as correct as the more advance tests, the book is just gives a general idea of what colours are affected by your vision, then you have the coloured disk test, put the pucks in the order of shade from one colour to the next. I failed the book tests ( was tested using 3 differerent test books to narrow down the colour problems, ) then I did the disk test and faile dit, but they rated me Cv2 for my personal safety, when on a call out at LFCA HQ I arranged to get a Latern test at DCIEM the same test they give pilots and i failed it badly was given the final CV3 rating for my personal safety.
There are many trades open to people who areCV3, just be prepared to look at a few other trades. Mostly likely you will find the following trade areas closed to you, most aircrew trade, naval hard sea trades, some tech trades, and some others. I remustered to Fin Clk now a closed trade but tht had nothing to do with me being colopur blind, just a choice. Still a lot of interesting trades left to you