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How can I style scale numbers in a Polar Area chart (chart.js)

I'm currently using a Polar Area chart from the chart.js lib, and I'm looking to style the scale numbers via CSS.
Below are two examples:
What it currently looks like:
What I want it to look like:
I'm not sure how to access those elements and apply CSS to them.
Some help to understand that process would be much appreciated.
Thanks! 😀

Charts.js produces a bit mapped image of a chart on a canvas element. Canvas elements are not subdivided into component elements that can individually styled using CSS (which is used for styling document elements in the DOM).
Styling of chart elements is actually achieved using canvas drawing options when the element is painted. Charts.js allows you to specify these.
A quick tour of documentation suggests you can specify the appearance of legend text using legend configuration options.
Worth looing into, the HTML legend call back may provide the means of making painted legends respond to CSS styling. See this related question Custom Legend with ChartJS v2.0

Merge two or more graphs using library

I am trying to make a dynamic graph something like as below:
Y-axis gives no. of users and x axis date range(For continuous graph )
x axis gives release of an algo on that date.(For discontinued graph)
I tried combined charts of highchart this and looked in google charts library.
Is there any way by how i can either directly generate a similar chart or merge two chart types in to one? Preferably using high charts or google graphs.
I guess we can merge two highcharts in to one but I am not very sure about it, also if we can Iam not sure how to do that.
Any help is appreciated.
Thanks

I am aware that you said "Preferably using high charts or google graphs", but I want to point out that this can be done very easily in C3.js using the "types" parameter to specify the graph type for each data item.
Demo: http://c3js.org/samples/chart_combination.html

I would suggest using plot bands to indicate release dates and types. You can dynamically add them using the addPlotBand() method (see http://api.highcharts.com/highcharts#Axis.addPlotBand). They would then overlay your "run of the mill" line chart showing number of users over time.
Assuming you have data that can distinguish between the release types, you could write code that adds a plot band of the desired color at the specific points on the x-axis.
I'd suggest making the plot bands have a from and to value thin enough (say, one interval or one date's worth) so it shows up as the thin stripes in your example.
You'd need to add a manual legend to show users what those colors mean, since plot bands wouldn't automatically show up in a Highcharts legend.
I hope this helps!

Providing gradient colours for google chart api to draw pie chart

I am using google chart APIs to draw a pie chart on the page. This uses some default colors to draw the sectors of the pie. We have an option to provide our own colors to draw the pie chart like colors:['red','#004411'] as suggested in https://google-developers.appspot.com/chart/interactive/docs/gallery/piechart. Now I want to know how can I achieve some glassy effect by providing gradient colors to the APIs? Is there any way with which I cant achieve this?

Already answered here. This is what it says:
It is not possible through standard configuration options for the new
SVG pie charts.
However, CSS can be used to color the elements of the pie chart if you
are in to that sort of thing. CSS can create gradients in various ways
depending on browser, etc. For more information on that, see this
site.
If you want to color a specific element of the pie chart, you can use
something like the developer tools in Google Chrome to help track down
a specific element, and recolor that element using CSS as above.
This will likely not work properly in IE (little does).
In general, however, the use of Gradients tends to just be eye candy,
and actually makes the chart more difficult to read (it doesn't much
matter for pie charts, which are generally not the best choice of
charts to begin with).

Which javascript or JQuery charting tool can I use to create heatmap charts with vertical column labels?

I'm looking for a charting library that can draw heatmap charts, and has the option of displaying column label text vertically (allowing me to fit lots of columns on the screen regardless of the length of the labels)
Ideally the library would be free for a charity/educational organisation.
Here's an example of a simple heatmap with vertical labels:
That chart was created using FusionCharts, which is not suitable as it is a flash-based product and is expensive to license.

You could always roll this yourself. Most of the table can be generated using ordinary HTML, with the exception of the vertical labels at the bottom. You could tackle that with Rafael, a JavaScript library that allows you to draw on an HTML canvas. Drawing rotated text is actually available out of the box so it won't be hard to implement.

I think what you are looking for is also called a TreeMap (in some circles anyway).
Check out thejit.org
Under the demos checkout the treemap and the icicle chart.

At this url you can find what you are looking for heatmapjs

Google Chart Visualization API, Bar chart values / tooltips

I am trying to add the actual value of all the bars in my chart to the
end of each bar. I want this to either replace, or to add to the tool-
tip functionality.
I see that this is possible in the image chart, it is the
functionality described in the following link that I wish to
replicate:
http://code.google.com/apis/ajax/playground/#image_bar_chart
I am wondering if this is possible in the Javascript based version of
the bar chart?
Many thanks,
H.

It looks like there's no built in functions to draw text ad-hoc on top of google's different charts. Behind the scenes, it's generating SVG so you could try to insert some valid SVG on your own.
Another option would be to use a more flexible (but less featureful) library like raphael.js:
http://raphaeljs.com/