1. appearing to be true, valid, or reasonable on the surface, though possibly not actually so
Usage: chiefly British spelling; American English typically uses 'colorable'
2. capable of being colored or dyed
Usage: less common; technical or specialized use

Examples

• The defendant offered a colourable excuse for missing the hearing.
• His argument had a colourable basis in law, though it ultimately failed.
• The company's claim to have reduced emissions was colourable but misleading.
• She presented a colourable reason for her absence, which the teacher accepted.
• The fabric is colourable and takes dye well.