Spiral galaxies are common in the universe. This example of the Pinwheel Galaxy M101 from the Hubble Telescope is found in Ursa Major, the Big Dipper.
About ⅔ of the spiral galaxies also have a feature in the center called a bar. This next example, also from Hubble, is known as NGC 1300. Some bars are very long and pronounced, as this one. Other galaxies have a bar that is quite short.
Notice in each galaxy the blue cast in the spiral arms. It comes from the glow of relatively young stars. Older stars tend to glow white, yellow, or orange. The vein-like structures are regions darkened by the absorption of dust.
I like to download greyscale images from the Hubble Legacy Archive site and try to combine them into color images. Hubble and other astro-imaging systems collect images in greyscale with their detectors. Filters of various wavelengths are placed in the light path. By using red-filtered, green-filtered, and blue-filtered images, they can be combined into an RGB color composite such as those above.
After selecting and downloading the 3 greyscale images, I open each in an app called FITS Liberator v4. Contrast and brightness are adjusted. The images are then saved as tif files labeled red, green, and blue. Next, the 3 tif images are opened in Photoshop Elements. Each greyscale is colorized into red, green, and blue versions. The green image is copy and pasted as a layer onto the red layer. The Blending Mode for the green layer is set to Screen so the green and red layers mix their colors. The blue image is copy and pasted as a layer onto the green layer with Blending set to Screen. Some adjustment might be needed to align the stars in the 3 layers.
My attempt for NGC 1300 is below. My choices of contrast and brightness for each greyscale image affects the final outcome of the colors of the RGB version. The Hubble images I chose were of the right half of the galaxy.
More examples of my attempts can be found here.