It is never too late to start painting. You don’t even have to quit your day job. All it takes is letting yourself enjoy incompetence. The less you know the faster you grow and the only way to learn is trial and error. Art schools, workshops and YouTube videos may give you some ideas on what to try but ultimately, you decide what works for you. The things that do not work when you experiment are important in learning process. If you don’t have enough of those, it means you are not taking enough chances.
Go to museums and galleries and see what impresses you the most, regardless of what other people like. Then figure out what it is specifically you like about a piece and try to use it as fuel to move forward. Practice is important and the way to put in the time it takes is staying excited about it.
Most of what you will learn has been around for ages. Instead of repackaging it, I have listed some of what you may find useful. The content here is compiled to remove some of the time or cost obstacles you may have in pursuing what makes you happy. However if those are not a problem, I do encourage you to find an artist you admire (both the person and the work) find out if the artist is also a good teacher and take a workshop with them. Supporting other artists living their dreams is a good thing. If you do take a workshop, take responsibility for what you want to learn. Study the artist work closely ahead of time and have your questions lined up before the first day.
Now let’s get to work.
Going to art store and looking at all the paint options can make you quit before you start. Starting with Limited Palette (4-5 colors) can reduce confusion. Mark Carder has a great videos on that approach:
Cesar Santos on Selecting Brushes.
Color perception - David Briggs has more details about various aspect of color on his website:
Glowing Light - You could paint along this simple study
Seeing edges - He uses a digital medium but principals apply to oil painting as well.
Here are a few reference materials you may find useful in getting started:
Color and Light by James Gurney
Oil Painting Essentials by Gregg Kreutz
Alla Prima II by Richard Schmid
The Artist's Handbook on materials and techniques (If you want to get technical)
Charles Bargue Drawing Course (If you want to practice forms)
Schools and Workshops
Groups and Societies