Let's say you have 1 cup of yellow paint and 1 cup of red paint. If you mixed the two cups together, you would have 2 cups of orange paint. If you mixed 1/2 cup of yellow paint with 1 cup of red paint, you would have a color that is more red than orange. Yes, "more deep" does the job. You can also say "deeper". There is no absolutely no difference in meaning between "more deep" and "deeper". Most people would say "deeper".

The first one is not really about the typical comparative rules or "more red" vs "redder". For me, what it is saying is "It's closer to being red in colour than it is to being orange". If you were comparing two red items, you would say "This object is redder than the other" OR "this object is more red than the other". For me, the second one must be "deeper"