Titanium has been on the market for ring bands for only a few years now. Yes, some of the bands combine gold with titanium. Titanium is an extremely light weight but quite durable and hard metal. Still, titanium will eventually scratch a little. Gold as an inlay or added "band" to the ring will wear much more quickly but may be more easily restored than can the titanium.
First, make sure you have white gold and not yellow. Both colors of gold are used as additions on titanium rings. To check, you need to clean any possible tarnish from the gold to see what the color truly is. White gold can turn a yellowish color but generally not so yellow as yellow gold. Use a paste of baking soda or a good jewelry polishing cloth of the type to remove tarnish and rub the ring. If white gold, the yellowish tarnish should come off and show the true color.
If not, likely the gold is yellow to start. Yes, the gold will look differently against titanium than with metals of other colors. I cannot say that white gold would look yellow since the rings I have seen look either yellow or white, depending on the original color of gold. White should look whiter, in my opinion.
Still, the white may be tarnished to a yellow tinge especially if of low karat such as 375. Generally, the gold applied to titanium in the usa is at least 14k, 585 and not the lower 9kt you mention. I assume you are in a British part of our world. If made for sale in the UK, 9kt is a possibility but generally the gold is of higher karat on titanium rings.
Refinshing the ring. Unfortunately, with the innate hardness of titanium even in jewelry alloys, home polishing will not restore the ring. You will need to visit a jeweler and ask that the ring be refinished. This is possible using aggressive buffing compounds on a motorized buffing machine. The compound must be aggressive to remove scratches from the hard metal. The jeweler must be quite careful to avoid too much polishing of the gold since that metal is much softer and could be buffed to a thin condition.
The jeweler will likely use a hard felt buffing wheel which will allow proper cutting of the titanium and is sharp edged enough to control the contact of the wheel with the gold section. The aggressive polishing is followed with finer compounds and lastly perhaps with a "green rouge" which will polish both the titanium and gold at the same time.
If the gold is white but tarnished to a yellow tinge, you may ask the gold area be plated with rhodium, a very hard and durable white metal often used to preserve white color in white golds. The jeweler may plate the gold only and avoid the titanium since you certainly do not want it to be plated with a white color!
This is done by masking or covering the titanium with a lacquer, red fingernail polish preferred since it is easy to see the start and end of the protective mask of lacquer. Then, using a simple electroplating bath, the rhodium is applied and will help keep the white gold white for a longer period of time. If after the first buffing to restore the luster, you may decide not to have the rhodium plate done. That is also a fine choice.
I am sorry there is not an "at home" remedy to repolish the titanium. The metal is simply too hard to polish without motorized buffing with the proper buffing wheel and polishing compounds. I do hope you enjoy the ring. Resizing is a problem and the titanium may be stretched or perhaps compressed about 1/2 finger size at the maximum. Cutting and adding or cutting to size down is not possible for the jeweler.