SAE30 is the right oil, and it is straw-coloured if it is clean, and gradually darkens as it gets dirtier, like any other engine oil. Red oil is usually automatic transmission fluid and is completely unsuitable, but there is nothing to stop an oil company from dyeing any oil red if they choose. I can't recall ever seeing any red SAE30 oil, so if you know someone with red oil in his mower engine, please tell us about it. Offhand I'd wonder if someone hasn't erroneously put ATF in his engine sump.
If you post the Model, Type and Code numbers of that Briggs and Stratton engine, we will be able to identify it. It does have a drain plug, but they aren't always easy to get at on ride-on mowers. Incidentally Victa does not make ride-ons, they buy them from major American manufacturers and sell them with the Victa brand attached.
My first guess is that the engine is a Model 219807, but we need to know for sure, so I can look it up in the manual. The 219807 is an Intek engine - Briggs' cheaper line of OHV mower engines. The drain plug is usually vertically mounted underneath the engine, so you'll have to crawl under to find it. Be sure and disconnect the spark plug before you do so, though.
