I'm trying to divide color space into 150-200 colors. I'm looking for Hex code/ RGB values and corresponding color name that is simple, well known & understandable by normal people. Is there any reference database I can use ?
No, best you can get is like 10–20 colors that people will agree a name on (some sources I've seen put this as low as 7). Even so, the variation is huge. But if you must bash your head at this then the XKCD color survey might be of interest to you.
150–200 recognizable color names is not going to happen. I mean you can name them but lo and behold even the most experienced people will have a hard time to distinguish the colors on their own. Best you can do is ask them to place colors in a relative order to each other.
In fact humans see color relative to other colors. So the same color next to a totally different color looks different! A classical example of this is the checkerboard shadow illusion. Under these condition its very hard to agree on a name.
Image 1: Checkerboard shadow illusion, the squares A and B have same color! (source)
Is the square A-B's color in image 1 dark gray or light gray? So for this reason any system you device is very artificial, humans will not really agree on it. So you must remind them.
The second reason is that variation of hex code across uncalibrated devices is quite a bit. Most users and devices fall into this category (>90%). Even so they would need to be watching in standard viewing conditions which is not going to happen. So even if you do name them by 200 different colors the color ranges might overlap on different monitors. So it's also not technically feasible to be accurate here. So if you want to be pedantic then you also need to define in what RGB space those hex values are defined in!
There are a few colour 'systems' that use names to identify the colours. The most obvious one being the Crayola Crayon Colours. Some of these are obvious like 'Lavender' while others are a bit more obscure, such as 'Tickle Me Pink'. Another example is the colour picker in MacOS which uses Crayons as a quick and easy away to select from a small range of colours. Some of these also have less obvious names like 'Ocean' and 'Bubblegum'.
You would not be able to use either of these systems as a whole because of copyright issues, but they might give you some inspiration to develop your own set of colour names. Also, you would be fine to use the obvious colours like 'Lavender', 'Violet' or 'Sepia' as these are established in common use.
There is also a nice (long!) list of colours on Wikipedia which are available under the Creative Commons License so you should be fine to use a subset of those colours if you wanted to.
I don't think you're going to find an 'off the shelf' solution to this problem, but building your own set of reference colours with names that invoke the correct colour to the average user shouldn't be too big a task.
Another color reference* is the color table of web colors (CSS color names that can be used instead of Hexadecimal values) http://www.w3schools.com/cssref/css_colors.asp The oficial w3 color table has less colors: https://www.w3.org/TR/css3-iccprof#x11-color
Some other color systems are Toyo and Munsell. You can even try painter's colour charts like winsor and newton: http://www.winsornewton.com/na/discover/resources/colour-charts/artists-oil-colour
But one note... *The fact that I am referencing another color reference is the crude reality that people do not agree on how the hell a color should be named.
So I totally agree on joojaa. You can not name more than a dozen colors, but even there people can not agree on that.
But an aditional problem is: An RGB color or an Hex value is not a color. It is an instruction to display a signal. But as you can see on any TV shop, some reds are redder on the neibourg's TV and the grass is always greener on the other side of the fence.
But for me, the best option in your case is stick to the CSS color chart and do not re-invent the wheel.
(An aditional note... I will never, ever learn thoose names and the exact hex values. But a name is a good starting point to have a rough idea on what the color is.)