There are several settings you can adjust to help fix streaky or missing colors when scanning.
Scanner Resolution: Setting the scanner resolution higher may improve the quality of the scanned image and reduce artifacting, such as streaks or missing colors. Higher resolutions can also result in larger file sizes, so it is important to find the balance between quality and file size.
Color Depth/Bit Depth: Increasing the color depth will allow for more accurate scans. A greater color depth, typically expressed as bits per pixel, gives more color information and can help reduce missing colors and artifacts.
Image Type: Scanning to a file type that is native to your scanner, such as the proprietary RAW or JPEG formats, can help reduce artifacts and improve the quality of the scanned image.
Brightness and Contrast: Adjusting the brightness and contrast of the image prior to scanning can help ensure that all of the details of the image are captured without streaking or missing colors.
Interpolation: Interpolation is a process where the scanner takes existing pixels and creates new ones to fill in missing or incomplete data. If enabled, this can help reduce scan artifacts such as missing or distorted colors. However, it can also cause an increase in file size, so it is important to balance the need for detail and clarity with the need for smaller file sizes.
Pre-scan Optimization: Many scanners have a pre-scan optimization feature which can help reduce the presence of artifacts when scanning. This can be used to reduce missing or distorted colors, as well as other scan artifacts.
Sharpening: Increasing the sharpness of the scan can help eliminate soft focus or blurry areas to reduce artifacts such as missing or distorted colors.
Noise Reduction: Some scanners include a noise reduction feature which can be used to reduce scan artifacts such as streaking or missing colors. Reducing noise can help improve the quality of the scan and reduce artifacts.
Scan Mode: Different scan modes can help reduce the presence of scan artifacts. For example, an RGB scan mode may reduce the presence of missing or distorted colors compared to a CMYK scan mode.
These are the basic settings that can be adjusted to help reduce the presence of streaky or missing colors when scanning. Depending on the scanner you have, there may be additional settings which can help improve the scan quality.