Red sandstone is sandstone appearing red due to the inclusion of iron oxides (hematite).
 Red Sandstone may also refer to:
Red Castle of Lunan is a ruined fortified house on the coast of Angus, Scotland.
 It is about 4 mi south-southwest of Montrose.
Lunan is a hamlet in Angus, Scotland, in the parish of the same name, 6 km south of Montrose.
 The hamlet overlooks Lunan Bay, which is itself also a hamlet, at the mouth of the Lunan Water.
 A 16th-century priest of Lunan church, which is in the hamlet of Lunan Bay, Walter Mill, was one of the last Scottish Protestant martyrs to be burned at St. Andrews.
 The church itself was rebuilt in 1844.
 The 15th-century Red Castle, so called from the red sandstone it is built from, is located 500 m to the south of the hamlet, on the south bank of the Lunan Water.
The New Red Sandstone is a chiefly British geological term for the beds of red sandstone and associated rocks laid down throughout the Permian (280 million years ago) to the end of the Triassic (about 200 million years ago) that underlie the Jurassic Lias; the term distinguishes it from the Old Red Sandstone which is largely Devonian in age.
The Bishop's Frome Limestone (or Bishops Frome Limestone) is a rock unit within the Raglan Mudstone Formation of the Old Red Sandstone occurring in the border region between England and South Wales.
 This limestone is a calcrete, that is to say it originated as a soil during a break in deposition rather than being an original marine deposit.
 It is perhaps the most significant of all of the calcretes which occur within the uppermost Silurian and lower Devonian sequence of rocks which constitute the Old Red Sandstone of the Anglo-Welsh Basin.
 It defines the boundary within the basin between the Silurian and the Devonian periods.
 The rock was formerly known as the Psammosteus Limestone after a characteristic fossil fish recorded from it; "Psammosteus anglicus".
 The fossil remains were subsequently shown to have been wrongly identified and belong in fact to "Traquairaspis symondsi".
 Its modern name derives from the Herefordshire village of Bishop's Frome.
 Its thickness is variable ranging from 2m up to 8m.
Inverness Castle (Scottish Gaelic: Caisteal Inbhir Nis) sits on a cliff overlooking the River Ness, in Inverness, Scotland.
 The red sandstone structure evident today was built in 1836 by architect William Burn.
 It is built on the site of an 11th-century defensive structure.
 Today, it houses Inverness Sheriff Court.
 There has been a castle at this site for many centuries.
 The castle itself is not currently open to the public, however a recent campaign has led to the creation of a working group to explore the possibility of doing so in the future.
 In April 2017 the north tower of the castle was opened to the public as a view point.
 At present, only the castle grounds and the north tower are open to the public.
The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age.
 It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America.
 It also extends northwards into Greenland and Svalbard.
 In Britain it is a lithostratigraphic unit (a sequence of rock strata) to which stratigraphers accord supergroup status and which is of considerable importance to early paleontology.
 For convenience the short version of the term, ORS is often used in literature on the subject.
 The term was coined to distinguish the sequence from the younger New Red Sandstone which also occurs widely throughout Britain.
Montrose Castle was a 12th-century castle built in Montrose, Angus, Scotland.
 Montrose was created a royal burgh by King David I of Scotland in the 12th century.
 The castle, once a royal castle, was built as a motte and bailey castle.
 King Edward I of England accepted John Balliol's surrender of Scotland at the castle on the 10 July 1296.
 The castle was destroyed by William Wallace in 1297.
 The castle was noted to be in ruins in 1488.
 Nothing now remains above ground.
The Flaming Mountains () or Gaochang Mountains are barren, eroded, red sandstone hills in Tian Shan Mountain range, Xinjiang, China.
 They lie near the northern rim of the Taklamakan Desert and east of the city of Turpan.
 Their striking gullies and trenches caused by erosion of the red sandstone bedrock give the mountains a flaming appearance at certain times of the day.
Abenhall is a small village in the English county of Gloucestershire, lying on the road between Mitcheldean and Flaxley in the Forest of Dean.
 The parish includes the settlement of Plump Hill, which is actually more populous than Abenhall itself, and was once part of the Hundred of St Briavels (known as Dene at the time of the Domesday book in 1086).
 Originally a mining and iron-making centre like much of the surrounding area, the village is notable for its 14th century Church of St Michael, which is built of local red sandstone and has ornate contemporary carvings relating to the Forest of Dean's principal industries.
 These include a shield bearing the arms of the Freeminers on the west wall and a mid-15th century octagonal font, that has tools of miners and metalworkers incised on its sides.
 Abenhall is a tiny, ancient village in a secluded quiet valley near Mitcheldean.
 The parish includes the settlement of Plump Hill, on the Mitcheldean to Cinderford Road as it climbs into the high Forest.
 Abenhall is on the Flaxley to Mitcheldean Road.
 Originally a mining and iron making centre, it is notable for its 14th century Church of St Michael, which is built of local red sandstone and has excellent contemporary carvings relating to the Forest of Dean's industries.
 These include a shield bearing the arms of the Freeminers on the west wall and the fabulous mid-15th century octagonal font, that has tools of miners and metalworkers incised on its sides.
 In the west tower is a spectacular new window installed 14 April 2011 by stained glass artist Thomas Denny; presented by the current free miners of the Forest of Dean to represent their gratitude and present day continuation of the ancient local customs of coal, iron ore and stone mining.

Question: Which castle south-southwest of Montrose is named after the red sandstone it's built from?
Answer: Red Castle