All ability scores increase by 1, or two ability scores increase by 1 (or one increases by 2 if you wish) and you take a feat.

Dragon Shifters mature at the same rate as their Humanoid half, but live as long as their Dragon half, which barring unfortunate events can be up to 1200 years of even longer.

A Dragon Shifter's size is that of their humanoid half. Use the size of whatever Humanoid race you base yourself off of.

Your movement speed is 30ft

You can see in dim light as if it were bright light for up to 60ft, and in darkness as if it were dim light. You cant discern color in darkness, only shades of gray. 

As a Dragon Shifter you have the ability to transform into a Dragon. Your Dragon form will get stronger as time goes on and the stronger you become, reflecting your strength as a person.

For this you will refer to page 90 in the Xanathar's Guide to Everything. When your player level vs the creature CR meets a 1:1 ratio you can hold that form indefinitely until your hp drops to zero and you revert to your humanoid form like a druid's wild shape ability. If you do NOT meet the 1:1 ratio then you can hold the form for a number of rounds equals to half of player level rounded up, plus con mod.  You can not transform into anything with a 3:1 ratio. To represent getting stronger with your form over time what you can do is take any dragon form (as there is at least 1 dragon in every CR) and alter it to meet your dragon type. Example: Green Dragon Wyrmling is CR 2. At level 7 you can hold a CR 3 dragon form, you could then take the stats of the Blue or Gold Dragon Wyrmling but replace its breath weapon damage type with that of the Green Dragon, as well as any resistances. You could also use this method to temporarily buff your Wyrmling form to that of a stronger Wyrmling for the allotted rounds based on player level plus con mod before reverting to the form of dragon you can maintain. (this method maybe be tedious to make changes to a different dragon every 1-2 levels to make it fit, but its that or a Green Dragon Shifter gets its Wyrmling form at level 5, and doesn't get to hold any stronger form until level 20, so I'd say its worth the hassle)

This ratio rule can be ignored for players up to level 4 as levels 1-3 you wouldn't be able to shift at all. in this case you get 1 transformation per long rest. Once you hit level 4 you meet a 2:1 ratio for the lowest CR Wyrmling and from that point on any 2:1 ratio CR transformations can be used a number of times equal to Con Mod per long rest.