On one of the drawings, use the eye-dropper tool.
You can select various color Sample Sizes, from 1 pixel to 101x101 Average.
Then double-click on the Color in the Color Palette, and add it to your swatches.
Give your new swatch a name.
Is this a cartton type image with large blocks of colour, or a photograph? There are two options towards the bottom of the Image > Adjustments menu. Replace Colour, and Match Colour. Both work well, but Match Colour might work better for you as it lets you choose colour from another image. Very easy to use, and very effective.
This is a cartoon type image with basically 2 colors. Orange and white. I need the orange part to be consistent.
Replace colour will work nicely then, but if you use the Eye droper sampler tool from the Eye dropper flyout, you can add a sample point to the source image which will record the value of the colour in the Info panel. This will give you a check to test the edited images to.