Map looks great. How did you do it?
Let me go over the steps mentally. I used GIMP 2.8; I prefer 2.6, but I think 2.8 is the new standard. Sorry if this is a bit lengthy and tutorial-ish, but I wanted to be comprehensive.
First, I reset all of Madras, Burma, and Malaya to solid blue/red as the base. I selected blue and red using the Fuzzy Select Tool (Hotkey U) and the Select By Color Tool (Hotkey: Shift+O). By holding shift while making the selection, I was able to add the various regions together. You can remove a region from selection by holding the ctrl key. The fuzzy select tool selects all similar colors from a contiguous region (say, if you used it on the main portion of Siam, it would select the continental portion, not the isthmus below). The Select By Color Tool selects all colors on the active layer that are the same (again, if used on Siam, for example, it would select all CSAS Blue on the map). Another tool that is useful is the temperature tool (Hotkey: O). This allows you to select the color of whatever you're hovering over. Holding ctrl will allow you to set your secondary color to that color instead of primary, but I find it's sometimes easier to just select one color at a time.
I selected the red that was on Madras, for example, with the Select By Color Tool. I then selected the pencil tool (N) and changed the brush from the fuzzy brush to a solid, circular brush. (Click on the Circle underneath opacity) This ensures that anything you pencil in will be entirely solid. To cover a large region, I'd suggest a brush about 6-10 pixels in size. This can be adjusted underneath the brush selection. Then, I colored over all the red in Madras with blue. I repeated the same steps for Burma and Malaya with the colors reversed.
Then, I selected Madras with the Fuzzy Select Tool. This had to be done twice, as there is one small portion east of Hyderabad that isn't contiguous on the image. After those regions of Madras and Ceylon (I forgot whether Ceylon was independent or part of Madras, but I included it therein as it was on the original alliance map) are selected, I picked a random pixel where I wanted to start. Make sure that your Pencil tool (N) has a size of 1 for this and the solid brush (i don't think it matters, but good policy to keep it the same).
Once you have the first pixel placed, hold shift. This allows you to create a line from the previously selected point to the next. After that, hold ctrl. This allows you to fix the angle of the line to built in designations. I believe 0, 15, 30, 45, 60, 75, and 90 degrees are the default ones. Once you have both held down and a 45 degree angle achieved, click again to draw a line between your starting point and the end point. Now, as only the regions of Madras/Ceylon were selected before, they are the only regions that have the red line on them.
From there, I just moved up 4 pixels and repeated the process. (I figured a 3 pixels of base color for every 1 pixel of alternate color is good for this case). Here, you have to do it by hand (there likely is a filter I don't know about). However, they are also easy to check; whatever the distance you choose, make sure it is the same between each line. I liked to just put my cursor over a pixel in the previous line and count up 4. Even if you're not over a selected square, it's ok: you can have an imaginary starting point in non selected space and have it overlap selected space.
This is also how you can line up the lines in Burma with Madras. Once done with Madras, deselect everything (Ctrl+Shift+A is the built in deselect all option; just think of it as the anti-select all of Ctrl+A) and then use the fuzzy select tool to select all the red of Burma. Make sure that only Burma is selected. Then, with Blue selected on your pencil tool (size 1 again), click on a line in Madras that you think would also be on Burma if extended across. With that imaginary starting point set, hold shift and ctrl, extend the line to Burma, and click again when it has covered the entire area. Then repeat making the lines 4 pixels apart once more. Continue on as you did for every successive case.
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All that said, have one correction and one suggestion. Correction was a pixel that was wrong just east of Hyderabad (which was my error on the previous part). I removed it. Secondly, here is (one) suggestion for a color for the A3. It isn't as bold as the rest of the other alliance colors, but it stands out from the neighboring 3 power blocs (most notably the Turin Pact and the Commonwealth). The only one it could be conflated with is the Orthodox Council, but they are far enough removed from one another that it should be an issue. (The Turkic League and the Turin Pact are far closer, and their colors stand out well enough).
Also... does the UK still maintain Bahrain in the Commonwealth? Saw that the pixel was there, but wasn't quite sure about whether it was the case or not.